UK Invoice Numbering with Custom Formats

Set invoice numbering inside the new-invoice form: click Format beside the invoice-number field, choose a preset or build a custom format, inspect the next-number preview and apply it. Every saved format keeps track of its own last invoice.

The practical advantage is running several numbering series at once. You can use INV-2026-001 for standard invoices and ONLINE-2026-001 for online-shop orders. Branches and other sales channels can be separated in the same way, with every format continuing from its own last-used number.

The button below opens a new invoice with the Format panel already displayed. You can reach the same panel manually through the Format button beside the invoice number. Numbers issued outside Simple Invoicing still need to be considered in your complete records.

Where to set the invoice number format

The format picker sits directly beside the invoice-number field in the new-invoice form.

1. 1

   Click Format beside the invoice number

   Open New invoice and find the Format button next to the invoice-number field. It opens the picker; the direct CTA on this page opens the same form with the picker displayed automatically.

2. 2

   Choose Presets or Custom format

   Select a ready-made pattern under Presets, or use Custom format to combine year, month, separators and one sequence. Add a custom text token for a prefix such as INV, ONLINE or a branch code.

3. 3

   Review Preview and click Apply

   The picker calculates the next value for that format. Apply inserts it into the invoice and associates the format with the saved document, allowing that series to continue independently next time.

Create a custom prefix and format

Open the Custom format tab and add tokens by clicking them. Use the custom text token for a prefix or suffix such as INV, ONLINE or a branch code, then add year, optional month, separators and one NN, NNN or NNNN sequence token.

The Preview changes as you build. After you click Apply and save the invoice, the format becomes available in recent History. You can also select a preferred format as the account default for future invoices.

• Use a prefix only when it helps your own records.
• Keep separators consistent across the series.
• Allow enough counter digits without making the number unreadable.
• Check the first invoice after a year or month change.

Run several numbering series at the same time

Invoices retain the format they used. When that saved format is selected again, Simple Invoicing finds its last compatible invoice and increments that sequence. The standard INV series therefore does not advance ONLINE, even when both are used from the same account.

GOV.UK includes a unique identification number in core invoice information. Check imported, manually edited and externally created invoices because the app cannot automatically see numbers kept only in another system.

A generator does not create your numbering policy

The format builder reduces typing and inconsistency, but it does not decide whether you need separate series or how corrections should be recorded. Agree those rules with the person responsible for your accounts and retain the records that support them.

Manual overrides, multiple systems and imports can still produce duplication. Always review the proposed number and search your existing invoice records when you are unsure.

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Frequently asked questions