Invoice Number Guide (2025)

ChiehCEO𝕏

Chieh is the founder of createinvoice.uk, where he shares practical insights on invoicing and business finance. With a focus on clarity and compliance, he helps readers understand how to set up invoice the right way.

Published on 25 August 2025

What is an invoice number?

An invoice number is a unique identification number for each invoice. It should be a sequential number ¹ based on one or more series which uniquely identifies the document.

It can include letters or numbers (such as the year), must be sequential but doesn't need to start from 1, and you can run multiple sequences simultaneously (for example, separate numbering for each customer or project).

Invoice Number Examples

Sequential Numbering
INV0001
Date-based Numbering
INV-2025-001
Customer-based Numbering
CUST-2025-001
Supplier-based Numbering
SUPP-2025-001

https://www.gov.uk/guidance/electronic-invoicing-notice-70063 ↩
https://www.gov.uk/hmrc-internal-manuals/vat-trader-records/vatrec5010 ↩

Invoice Number Guide (2025)

What is an invoice number?

Invoice Number Examples

FAQ

Still Have Questions?

References

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Invoice Number Guide (2025)

What is an invoice number?

Invoice Number Examples

FAQ

Is an invoice number mandatory in the UK?

Can invoice number include letters?

Can I start invoice number from 3305, not 1?

I have several customers and I wish to run several separate sequences of invoices at the same time. Is this possible?

What happens if there's a gap in my invoice sequence due to cancelled or spoiled invoices that were never issued?

Still Have Questions?

References

Footnotes

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