# How to Write an Invoice: Every Field, With an Example

To write an invoice, give it a unique number and date, name both parties, list what you supplied with quantities and prices, show tax separately, and state the total, due date and how to pay. Here is each field in order, with a fully worked example.

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- **Canonical URL:** https://dothecalculation.com/blog/business/how-to-write-an-invoice
- **Category:** Business
- **Author:** Do The Calculation Team
- **Published:** 2026-09-21
- **Reading time:** 23 min read
- **Publisher:** Do The Calculation (https://dothecalculation.com)
- **Methodology:** https://dothecalculation.com/methodology

---

## How do you write an invoice?

Write an invoice by giving it a unique invoice number and an issue date, then adding your business details and your customer’s, a line for each thing you supplied (with quantity, unit price and amount), any tax shown separately, the total, the balance due, the due date and how to pay. Then send it as a PDF.

Below, each field is taken in the order you fill it in, then one complete invoice is built with every number shown, followed by what five tax authorities say a valid invoice must contain, how to send it and how long to keep it.

Tool: [Fill in each field as you read](https://dothecalculation.com/tools/invoice-generator) — The free invoice generator has every field in this guide, works in your browser with no sign-up, and downloads a PDF without a watermark.

One boundary first. Tax rules differ by country, by region and by what you sell. This is general information about how invoices are built and what the published rules say, not tax or legal advice for your business. Where a rule matters, the source is linked so you can read it yourself.

## Step by step: every field in the order you fill it

Most invoice layouts put the fields in roughly the same places: your details and logo at the top, the customer and the dates below, a table of lines in the middle, totals at the bottom right, and payment details and notes underneath. Filling them in that order means you never have to go back.

_[Figure: The order to fill in an invoice — Each step depends only on the ones before it, so working top to bottom avoids rework.]_

### 1. The document title and invoice number

The title tells the reader what kind of document this is. “Invoice” is the default. In Australia a GST-registered business uses the words “tax invoice”, and some businesses elsewhere use “Tax Invoice” when the document is meant to support the customer’s tax reclaim. A “Proforma Invoice” is a different thing: an advance copy that asks for nothing yet. The differences between these, and between an invoice, a quote and a receipt, are covered in [invoice vs receipt vs quote](/blog/business/invoice-vs-receipt-vs-quote).

The number must be unique, and under both UK VAT rules and the EU VAT Directive it must be sequential, “based on one or more series”. That wording matters: you may run separate series, such as one per year (2026-0001, 2026-0002) or one per shop, as long as no number appears twice and each series runs in order. Never reuse a number after cancelling an invoice. Cancel it with a credit note and issue a new one.

A format that holds up is a short prefix, the year, and a four-digit counter: HPC-2026-0142. It sorts correctly in a file list, tells you the year at a glance and leaves room for 9,999 invoices a year. You do not have to start at 0001. Starting a new business at, say, 0101 is common and harmless, provided you then count up without skipping or repeating.

### 2. Your business details

Put the name the customer has in their supplier records. In the UK, GOV.UK says a sole trader must show their own name and any business name they use, and, if they trade under a business name, an address where legal documents can be delivered. A limited company must show its full name as it appears on its certificate of incorporation, and if it names any director on the invoice it must name all of them.

Then add an address, an email address and a phone number someone answers. If you are registered for VAT, GST or a similar tax, your registration number belongs here: it is required on a UK VAT invoice, an EU VAT invoice and an Australian tax invoice (as your ABN), and a Canadian GST/HST registrant’s number is needed on invoices of $100 or more for the customer to claim input tax credits. A logo is optional; it helps the invoice get recognised in a crowded inbox, but it has no legal weight.

### 3. The customer

Bill the legal entity that owes you the money, not the person you dealt with. If you worked with Sam at a café that trades through a limited company, the invoice goes to the company’s registered name, with “Attn: Sam Okafor” underneath. An invoice made out to the wrong entity is one that accounts can legitimately refuse to process.

Include the customer’s address. Add their VAT number when the rules need it: the EU list includes the customer’s VAT number where the customer is liable for the tax. Australian tax invoices for sales over $1,000 must show the buyer’s identity or ABN, and Canadian invoices of $500 or more need the buyer’s name for the customer to claim input tax credits.

### 4. Dates and references

There are up to three dates on an invoice, and people mix them up. The issue date is the day you create the invoice. The supply date is when you delivered the goods or finished the work; GOV.UK lists it as a required item, and on a UK VAT invoice the “time of supply” is required too. The due date is when payment must arrive.

The due date comes from your payment terms. “Net 30” means payment is due 30 days after the invoice date, so an invoice dated Monday 21 September 2026 on Net 30 is due Wednesday 21 October 2026. Print the actual date, not just “Net 30”, because a date is harder to misread. What each term means, and which to choose, is the subject of [invoice payment terms explained](/blog/business/invoice-payment-terms-explained). In the UK, if no payment date is agreed, GOV.UK says payment is late 30 days after the customer gets the invoice or the goods or service.

References come last in this block. If the customer gave you a purchase order number, it must be on the invoice, usually right next to the invoice number. Many larger organisations match every invoice to a purchase order automatically, and an invoice without one can sit unmatched until someone notices. Add any other reference the customer asked for: a project code, a cost centre, a contract number.

### 5. Line items

Each line needs a description someone else can understand, a quantity, a unit, a unit price and an amount. “Services — $1,200” fails the description test. “Brand refresh: logo redraw and colour palette, 3 rounds of revisions (per quote Q-2026-031)” passes it. Accounts staff are often approving work they never saw, and a specific description is what lets them approve it without emailing you first.

Use units that match how you priced it: hours, days, pieces, boxes, square metres. A unit price is required on a UK VAT invoice and in the EU list, where it must be shown before tax. If a line is discounted, show the discount on the line rather than silently lowering the price, so the customer can see the saving you gave them. If some lines are taxable and some are not, mark which is which; both the Australian and Canadian rules require an invoice to make clear which supplies on it are taxable when it mixes them.

### 6. Totals

The totals block runs top to bottom in a fixed order: subtotal of the lines, any invoice-wide discount, shipping or fees, tax (one row per rate), the invoice total, any deposit or amount already paid, and finally the balance due. The balance due is the one figure the customer actually pays, so make it the largest number on the page.

**The totals block, in order**

```
Subtotal − invoice discount + shipping + tax = Total   ·   Total − amount already paid = Balance due
```
- Tax is calculated on the taxable lines only, after discounts, not on the whole subtotal.
- Each money amount is rounded to 2 decimal places (half away from zero) before it is added.
- If more has been paid than is owed, the balance becomes a credit in the customer’s favour.

### 7. How to pay, and the notes

State exactly how to pay: bank name, account name, account number and sort code or routing number, or IBAN and BIC for international payments. Ask the customer to use the invoice number as the payment reference, so the money can be matched when it lands. If you accept cards through a payment provider, include the link you already use with that provider.

Notes are for anything that helps the invoice get paid or explains a number: a thank-you, what the deposit covered, a short statement of your terms, or a reverse-charge wording when the customer accounts for the tax. Keep them short. Long terms and conditions belong in your contract, with the invoice pointing to them.

### 8. Check, save and send

Before sending, add the lines up yourself once, check the due date against a calendar, and check that the customer’s name matches their records. Save the final version before it goes out, because the copy you keep must be the one the customer received. Sending is covered in its own section below.

## A complete invoice example, worked line by line

Here is one invoice built from start to finish. The business and the customer are made up, and so is the tax rate: say a small sign and print shop, Harbour Print Co., works in a US state with a combined sales tax rate of 8%, and in that state (as in this example only) design and installation labour are not taxable while printed goods are. Your rate and your taxable categories will differ, so check them with your state or local tax authority.

Harbour Print Co. has made new menu boards, pavement signs and business cards for a café, designed them, and installed the boards on Friday 18 September 2026. The café paid a $400.00 deposit when it approved the quote. The shop agreed Net 30 terms and the café issued purchase order PO-7713.

**Header of the example invoice**
| Field | What goes in it |
| --- | --- |
| Title | Invoice |
| Invoice number | HPC-2026-0142 |
| From | Harbour Print Co., address, email, phone, sales tax permit number |
| Bill to | The café’s registered company name and billing address, Attn: the owner |
| Issue date | Monday 21 September 2026 |
| Supply date | Friday 18 September 2026 (installation completed) |
| Payment terms | Net 30 |
| Due date | Wednesday 21 October 2026 |
| PO number | PO-7713 |

**Line items and totals (sales tax at a hypothetical 8% on taxable lines only)**
| Line | Qty | Unit | Unit price | Discount | Taxable | Amount |
| --- | --- | --- | --- | --- | --- | --- |
| Menu boards, A2, printed and laminated | 6 | each | $45.00 | — | Yes | $270.00 |
| A-frame pavement sign, double-sided | 2 | each | $189.50 | 10% | Yes | $341.10 |
| Business cards, 350gsm, box of 250 | 4 | box | $32.75 | — | Yes | $131.00 |
| Design and artwork preparation | 3.5 | hour | $65.00 | — | No | $227.50 |
| Installation of menu boards on site | 1 | visit | $80.00 | — | No | $80.00 |
| Subtotal |  |  |  |  |  | $1,049.60 |
| Taxable amount |  |  |  |  |  | $742.10 |
| Sales tax 8% |  |  |  |  |  | $59.37 |
| Total |  |  |  |  |  | $1,108.97 |
| Less deposit paid |  |  |  |  |  | −$400.00 |
| Balance due by 21 Oct 2026 |  |  |  |  |  | $708.97 |

### Where each number comes from

- Menu boards: 6 × $45.00 = $270.00.
- A-frame signs: 2 × $189.50 = $379.00 before discount. The 10% discount is $37.90, so the line is $379.00 − $37.90 = $341.10.
- Business cards: 4 × $32.75 = $131.00.
- Design: 3.5 × $65.00 = $227.50. Half hours are fine as a quantity; write 3.5, not “3h30”.
- Installation: 1 × $80.00 = $80.00.
- Subtotal: $270.00 + $341.10 + $131.00 + $227.50 + $80.00 = $1,049.60.
- Taxable amount: only the three printed-goods lines, $270.00 + $341.10 + $131.00 = $742.10. The two labour lines, $307.50 in total, are left out.
- Sales tax: $742.10 × 8% = $59.368, which rounds half away from zero to $59.37.
- Total: $1,049.60 + $59.37 = $1,108.97.
- Balance due: $1,108.97 − $400.00 deposit = $708.97.

> **The error the taxable column prevents** — Charging 8% on the whole $1,049.60 subtotal would give $83.97 of tax instead of $59.37, overcharging the café by $24.60. The café would be right to query it, and fixing it means a credit note and a new invoice rather than a quick edit.

Below the totals, Harbour Print Co. would put its bank details, the line “Please use HPC-2026-0142 as your payment reference”, and a one-line note: “Deposit of $400.00 received 2 September 2026 against quote Q-2026-088.” That note answers the first question the café’s bookkeeper would otherwise ask.

If you want to check an example like this yourself, the [sales tax calculator](/calculators/sales-tax-calculator) handles the tax line, and the [discount calculator](/calculators/discount-calculator) handles a percentage off a line. The same layout in a spreadsheet, with SUMIFS doing the taxable subtotal, is in the [Excel invoice template with tax](/blog/templates/excel-invoice-template-with-tax).

## How tax, discounts and deposits interact

Three situations change the arithmetic above, and each is easy to get wrong the first time.

### An invoice-wide discount on a mixed invoice

A discount on one line only reduces that line. A discount on the whole invoice has to be shared between the taxable and non-taxable lines, or the tax is wrong. The usual method is to split it in proportion to each part’s share of the subtotal. On the example, a hypothetical $50.00 invoice discount would reduce the taxable part by $50.00 × 742.10 ÷ 1,049.60 = $35.35, leaving a taxable amount of $706.75 and tax of $56.54, and a total of $1,056.14.

### Prices that already include tax

If you sell at tax-inclusive prices, the tax is extracted from the total rather than added to it: tax = price × rate ÷ (1 + rate). At a 10% rate, a $110.00 sale contains $10.00 of tax, not $11.00, because $110.00 × 0.10 ÷ 1.10 = $10.00. Working backwards by taking 10% off the total is the common mistake. Whichever way you price, show the tax as its own figure or state clearly that the total includes it, which is the choice the Canadian rules explicitly allow. The [GST calculator](/calculators/gst-calculator) and [VAT calculator](/calculators/vat-calculator) do both directions.

### Deposits and part payments

A deposit does not reduce the invoice total or the tax on it; it reduces the balance due. The final invoice shows the full value of the work, the full tax, and then “Less deposit paid”. If you issued a separate invoice for the deposit itself, reference its number here. How deposits and stage payments fit into your terms is covered in [payment terms explained](/blog/business/invoice-payment-terms-explained), and freelancer billing models such as milestones and retainers are in [how to invoice as a freelancer](/blog/business/how-to-invoice-as-a-freelancer). When the deposit arrives, confirm it with a numbered receipt from the [receipt maker](/tools/receipt-maker); if the job began with a quote, the [estimate and quote generator](/tools/estimate-generator) turns the accepted quote into an invoice with the lines already filled in.

> **A credit is its own document** — If you need to reduce an invoice you have already sent, do not edit it and send it again under the same number. Issue a credit note that references the original, with negative amounts, so both of your records and the customer’s still add up.

## What must a valid invoice show? UK, EU, Australia, Canada and US

The fields in the walkthrough above satisfy most rules, but the details differ, and the stricter lists apply only once you are registered for VAT, GST or HST. This table summarises what each authority’s own published guidance says. It is a summary, not the full rule: read the linked source for your country, and check local or state rules that sit on top of it.

**What the published rules require, by jurisdiction (checked September 2026)**
| Where | Applies to | What the invoice must show | Worth knowing |
| --- | --- | --- | --- |
| UK (any business) | All invoices | Unique ID number; your name, address and contact details; customer’s name and address; clear description; supply date; invoice date; amounts charged; VAT if applicable; total owed | Sole traders using a business name add their own name and an address for legal documents; limited companies use the full registered name |
| UK (VAT registered) | VAT invoices, required when you and your customer are both VAT registered | Sequential number; time of supply; issue date if different; your name, address and VAT number; customer’s name and address; description; quantity or extent, VAT rate and amount excluding VAT per line; total excluding VAT; unit price; rate of any cash discount; total VAT in sterling | Normally issue within 30 days of the supply; a simplified invoice is allowed for £250 or less including VAT |
| EU (VAT Directive) | Most business-to-business supplies and some consumer sales | Issue date; sequential number; supplier’s VAT number; customer’s VAT number where the customer is liable for the tax; both full names and addresses; quantity and nature of the goods or services; supply date; taxable amount per rate, unit price excluding VAT and any discounts; VAT rate; VAT amount | Add “Reverse charge” where the customer accounts for the VAT; amounts may be in any currency but the VAT must also be shown in the member state’s currency |
| Australia (GST registered) | Tax invoices, required for taxable sales over $82.50 including GST, or when a customer asks | The words “tax invoice”; your business name and ABN; issue date; description including quantity and price; GST payable, if any | Sales over $1,000 must also show the buyer’s identity or ABN; a requested tax invoice must be given within 28 days |
| Canada (GST/HST registrant) | Information the customer needs to claim input tax credits | Under $100: supplier name, date, total. $100–$499.99: add your GST/HST registration number and the tax charged (or a statement that prices include it). $500 or more: also the buyer’s name, a description and the payment terms | If an invoice mixes taxable and exempt items, it must show which is which from $100 upwards |
| United States | Federal income tax records | The IRS does not publish a required invoice layout; it lists invoices among the documents that support gross receipts | If you collect sales tax, check your state’s revenue department for what a sales invoice must state |

Two patterns stand out. First, the detailed lists exist to protect the customer’s right to reclaim tax. A VAT-registered customer in the UK or EU, a GST-registered customer in Australia or an HST registrant in Canada needs your invoice to carry certain fields before they can claim back the tax they paid you, which is why a missing registration number can hold up a payment even when the work was perfect.

Second, the lists overlap heavily: who, to whom, when, what, how much, and how much tax. The country-specific additions are small: a registration number, a “tax invoice” title in Australia, a sterling VAT total on a UK VAT invoice issued in another currency, a “Reverse charge” note where an EU customer accounts for the VAT.

> **Not registered for tax? Do not show any** — If you are not registered for VAT, GST or HST, you cannot charge it, so the invoice should not have a tax line or call itself a tax invoice. In Australia, business.gov.au notes that businesses not registered for GST do not have to give regular invoices at all, but says it is good practice. For how the tax side works once you are registered, see [GST and sales tax compliance](/blog/business/gst-sales-tax-compliance).

## Mistakes that delay payment

Most late payments are not refusals. They are invoices that got stuck somewhere between the inbox and the payment run, usually because something on them did not match what the customer’s process expected. These are the causes worth checking before you press send.

**What goes wrong, what the customer does, and the fix**
| Mistake | What happens on the customer’s side | Fix |
| --- | --- | --- |
| Missing purchase order number | The invoice cannot be matched and waits in an exceptions queue | Ask for the PO before you start the work and put it next to the invoice number |
| Billed to the wrong entity | Accounts has no supplier record for that name and returns it | Use the legal name from the contract or PO, with the contact as “Attn:” |
| Sent to your contact only | The contact forwards it days later, or forgets | Send to the accounts payable address and copy your contact |
| Vague descriptions | The approver emails to ask what it is for, and the clock pauses | Describe the deliverable and quote the quote or project reference |
| Tax on the wrong lines, or no registration number | A registered customer cannot reclaim the tax and asks for a corrected invoice | Mark each line taxable or not, and show your number |
| Arithmetic that does not add up | The invoice is rejected or queried in full | Round each line, then total the rounded lines |
| No due date, only “Net 30” | The customer counts from when they received or approved it | Print the actual due date |
| No payment details or reference | Money arrives without a reference and is not matched to you | Include full bank details and ask for the invoice number as reference |
| Duplicate invoice number | The payment system flags it as a duplicate and blocks it | Keep one numbering series and never reuse a number |
| Invoicing late | Your invoice lands after their month-end cut-off and misses a payment run | Invoice the day the work is delivered, or on the agreed date |

The last row is the one most within your control. Payment terms start from the invoice date, so every day between finishing the work and sending the invoice is a day added to how long you wait. On Net 30, an invoice sent two weeks late is effectively Net 44.

If the invoice is right but still unpaid after the due date, that is a different job: [chasing overdue invoices and charging late fees](/blog/business/overdue-invoice-follow-up-and-late-fees) sets out a reminder schedule and the statutory interest rules.

If you invoice regularly, it is worth tracking how long customers actually take to pay. The [days sales outstanding calculator](/calculators/days-sales-outstanding-calculator) turns your receivables and sales into an average collection time, which is the number that tells you whether your terms are being respected.

## How to send an invoice

Send a PDF. It looks the same on every device, it cannot be edited by accident, and it is what most accounts teams expect to receive and file. A Word document or a spreadsheet can reflow or be altered, and a link to a web page may not be accepted by a customer whose process requires an attached document. In the EU, the European Commission notes that electronic invoices are treated the same as paper ones, subject to the customer accepting them.

### Who to send it to

Ask at the start of the job: “Who should invoices go to, and do you need a PO number?” Small businesses often want the invoice sent to the owner. Larger ones usually have an accounts payable address, and some have a supplier portal where invoices must be uploaded instead. Send to the address they give you and copy your day-to-day contact, who can approve it quickly.

### The subject line and the email

Put the three facts someone searching their inbox will need into the subject line: invoice number, your business name, and the amount and due date. For the example above, that is: “Invoice HPC-2026-0142 from Harbour Print Co. – $708.97 due 21 Oct 2026”.

The body should be short enough to read without scrolling: a greeting, one line on what the invoice is for, the balance and due date again, the PO number if there is one, how to pay, and who to contact with questions. For example: “Hi Maria, please find attached invoice HPC-2026-0142 for the menu boards, signs and business cards installed on 18 September, against PO-7713. The balance after your deposit is $708.97, due by 21 October 2026. Bank details are on the invoice; please use the invoice number as the reference. Thanks again for the work.”

- Name the file so it survives being saved: HPC-2026-0142-Harbour-Print-Co.pdf, not invoice.pdf or scan001.pdf.
- Send one invoice per email unless the customer asks for batches. A single email with five attachments is easy to half-process.
- Keep the email and the PDF consistent. If the amount in the email differs from the attachment, the invoice will be queried.
- Send it on the day the work is delivered, or on the agreed billing date, not whenever you next get round to admin.

The invoice generator on this site creates and downloads the PDF but does not send email, so you attach the file to a message from your own email account. That also means the invoice comes from an address the customer already recognises.

## How long should you keep invoices?

Keep a copy of every invoice you issue, and every invoice you receive, for at least as long as your tax authority can ask to see it. The periods below come from each authority’s own guidance; several have longer periods for special cases, so treat them as minimums.

**Minimum record-keeping periods in the published guidance**
| Where | Who | Keep records for |
| --- | --- | --- |
| UK | Sole traders (Self Assessment) | At least 5 years after the 31 January submission deadline of the tax year |
| UK | Limited companies | 6 years from the end of the last company financial year they relate to, longer in some cases |
| UK | VAT-registered businesses | Generally at least 6 years |
| US | Federal income tax (IRS) | 3 years generally; 6 years if you under-report income by more than 25% of the gross income shown; 7 years for a bad debt or worthless securities claim; indefinitely if no return or a fraudulent return is filed |
| Canada | Businesses (CRA) | Generally 6 years from the end of the last tax year they relate to |
| Australia | Businesses | Most business records for at least 5 years |

The UK sole trader rule counts from a deadline, not from the invoice date, which makes it longer than it sounds. Take an invoice dated 21 September 2026. It falls in the 2026 to 2027 tax year, whose online return is due by 31 January 2028, so the record must be kept until at least the end of January 2033, more than six years after the invoice was written.

Keep the invoice exactly as sent, as a PDF, together with the record of payment. Australian guidance explicitly accepts printed or electronic records, and the EU treats electronic invoices as equal to paper ones; wherever you are, a copy that only exists inside one app or one browser is fragile. Export your invoices to a folder you back up, named by invoice number so they sort in order.

> **Where the invoice generator keeps your data** — The invoice generator saves your invoices and clients in your browser’s local storage, not on a server. That keeps them private, but clearing the browser’s site data deletes them. Use its JSON backup export regularly, and keep the downloaded PDFs somewhere backed up as your actual records.

Tool: [Build the worked example yourself](https://dothecalculation.com/tools/invoice-generator) — Enter the five lines, tick which are taxable, add the 8% tax and the $400 deposit, and check the balance comes to $708.97 before you download the PDF.

## Sources

- GOV.UK, what a UK invoice must include, including sole trader and limited company rules and when VAT invoices are needed: https://www.gov.uk/invoicing-and-taking-payment-from-customers/invoices-what-they-must-include
- HMRC VAT Notice 700/21, full VAT invoice contents, the £250 simplified invoice limit, issuing within 30 days, VAT in sterling and keeping VAT records for 6 years: https://www.gov.uk/guidance/record-keeping-for-vat-notice-70021
- GOV.UK, late commercial payments, when a payment is late if no date is agreed: https://www.gov.uk/late-commercial-payments-interest-debt-recovery
- GOV.UK, how long sole traders must keep records, with the worked deadline example: https://www.gov.uk/self-employed-records/how-long-to-keep-your-records
- GOV.UK, how long limited companies must keep accounting records: https://www.gov.uk/running-a-limited-company/company-and-accounting-records
- European Commission, VAT invoicing rules, full and simplified invoice contents, when an invoice is compulsory and electronic invoices: https://taxation-customs.ec.europa.eu/taxation/vat/vat-businesses/invoicing_en
- Council Directive 2006/112/EC, Articles 226 (invoice contents, including “Reverse charge”) and 230 (currency), as published on legislation.gov.uk: https://www.legislation.gov.uk/eudr/2006/112/title/XI/chapter/3/2020-01-31/data.xht?view=snippet&wrap=true
- business.gov.au, how to invoice, including tax invoice contents, the $82.50 and $1,000 thresholds, the 28-day rule and keeping records for 5 years: https://business.gov.au/finance/payments-and-invoicing/how-to-invoice
- Canada Revenue Agency, input tax credits, the information requirements chart for invoices under $100, $100 to $499.99 and $500 or more: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/gst-hst-businesses/calculate-prepare-report/input-tax-credit.html
- Canada Revenue Agency, how long to keep business records: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/keeping-records/where-keep-your-records-long-request-permission-destroy-them-early.html
- IRS, what kind of records to keep, listing invoices as support for gross receipts: https://www.irs.gov/businesses/small-businesses-self-employed/what-kind-of-records-should-i-keep
- IRS, how long to keep records: https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records

## Where to go next

Once the invoice itself is right, the next decision is the terms printed on it: [invoice payment terms explained](/blog/business/invoice-payment-terms-explained) covers Net 30, early-payment discounts and deposits. If an invoice goes past its due date, [overdue invoice follow-up and late fees](/blog/business/overdue-invoice-follow-up-and-late-fees) has the reminder schedule and the interest calculations.

Not sure whether you need an invoice, a quote or a receipt? [Invoice vs receipt vs quote](/blog/business/invoice-vs-receipt-vs-quote) sorts out every document in the sales cycle. And if you bill for your own time, [how to invoice as a freelancer](/blog/business/how-to-invoice-as-a-freelancer) goes through hourly, day-rate, fixed-price and retainer billing, with the [freelance rate calculator](/calculators/freelance-rate-calculator) to set the rate itself.

The documents on either side of the invoice have their own guides. Before the work, [how to write an estimate](/blog/business/how-to-write-an-estimate) prices a job line by line. After payment, [how to write a receipt](/blog/business/how-to-write-a-receipt) covers what the proof of payment should show.

## Common questions

**What is the minimum an invoice must include?**

At a minimum: a unique invoice number, the invoice date, your name and address, the customer’s name and address, a description of what you supplied, the date you supplied it, the amounts charged, any tax, and the total owed. That is essentially the GOV.UK list, and it covers the core of most countries’ rules. Tax-registered businesses need extra fields, such as their registration number.

**Can I write an invoice if I am not registered for VAT or GST?**

Yes. Anyone who sells goods or services can issue an invoice. What you cannot do is charge VAT, GST or sales tax you are not registered to collect, so leave the tax line off and do not title the document “Tax Invoice”. Show your name, the customer, the work, the amount and how to pay, and keep a copy for your own tax records.

**Does an invoice number have to be sequential?**

For VAT invoices in the UK and EU, yes: the rules call for a sequential number based on one or more series that uniquely identifies the invoice. You can run separate series, for example one per year, as long as each runs in order and no number is used twice. Even where it is not required, a sequence makes gaps and duplicates easy to spot.

**What is the difference between the invoice date and the supply date?**

The invoice date is when you issue the invoice. The supply date is when you delivered the goods or completed the service. They are often the same day, but not always, for example when you invoice on Monday for work finished on Friday. GOV.UK lists both as required on UK invoices, and a UK VAT invoice must show the time of supply.

**Should I add tax to every line on the invoice?**

Only to lines that are taxable where you sell them. Many invoices mix taxable goods with services or items that are exempt or not taxed, and the tax should be calculated on the taxable lines only. Mark each line so the customer can see which were taxed. Charging tax on the whole subtotal overcharges the customer and means a corrected invoice later.

**How do I show a deposit on the final invoice?**

Show the full value of the work and the full tax first, then a line “Less deposit paid” with the amount and, ideally, the date and the deposit invoice number. The balance due is the total minus the deposit. The deposit does not reduce the taxable amount, because it is a payment towards the invoice, not a discount on it.

**Is it better to send an invoice as a PDF or in the email body?**

Attach a PDF. It keeps its layout on every device, is hard to alter by accident, and gives the customer a document to file and match against a payment. Put the invoice number, amount and due date in the email as well, so the message is useful even before the attachment is opened, and name the file after the invoice number.

**Can I change an invoice after I have sent it?**

Do not edit and resend it under the same number, because the customer may already have recorded the original. To reduce or cancel it, issue a credit note referencing the original invoice number. To charge more, issue an additional invoice. That keeps both sets of records consistent and leaves a clear trail if either of you is ever asked to explain it.

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_Source: [Do The Calculation](https://dothecalculation.com/blog/business/how-to-write-an-invoice). Quote freely with attribution and a link to this page._