Master data clean-up for e-invoicing: VAT numbers and more

Master data clean-up is the least glamorous and most important part of e-invoicing preparation. Before April 2029, check every in-scope customer and supplier record for a valid VAT number, correct legal name and address, a confirmed Peppol ID, and the references and VAT codes your invoices need. Bad data that a person would correct without thinking will cause e-invoices to fail validation or go to the wrong place.

You can start this today. None of it depends on the UK specification, which is expected from the Budget 2026 roadmap on 28 October 2026.

Why data quality matters more with e-invoicing

With PDFs, a person reads the invoice and fixes small problems. With e-invoices:

• software looks up the customer's Peppol ID to decide where to send the invoice, so a wrong ID means a wrong or failed delivery;
• validation rules check that totals, VAT breakdowns and codes are consistent, so an unmapped tax code can stop an invoice;
• buyers' systems match automatically on PO number, supplier identity and amounts, so missing references lead to rejections;
• duplicates can mean an invoice is delivered to an old entity or a supplier is paid twice.

Peppol is confirmed as the UK network; the GOV.UK Tax update 2026 summary says it "will be the core interoperability network for e-invoicing in the UK". Every Peppol exchange relies on accurate identifiers.

What to clean, field by field

Field	Check	How
Legal name	Matches the registered legal entity, not a trading name	Compare with VAT check result and contracts
Address	Current registered or business address	Compare with VAT check result
UK VAT number	Valid and belongs to this entity	HMRC Check a UK VAT number
Number format	Stored consistently, for example "GB" plus nine digits, no spaces	Standardise in your system
XI number	Recorded where a Northern Ireland business uses one	See below
Peppol ID	Scheme and value confirmed with the partner or directory	Peppol Directory lookup
Duplicates	One record per legal entity	De-duplicate on VAT number and company number
PO and buyer reference rules	Which customers require which references	Ask customers; see buyer reference BT-10
VAT codes	Every tax code maps to a VAT category code	Mapping table
Units of measure	Mapped to standard codes	Mapping table
Bank details	Verified independently	Your usual fraud controls
Invoice contacts	Named person or mailbox	Ask partners

VAT numbers: the core of the clean-up

HMRC's Check a UK VAT number service confirms whether a UK VAT number is valid and shows the name and address of the business it is registered to. If you are VAT-registered, you can also use it to prove when you checked a number. For EU numbers, GOV.UK points to the EU's VIES service.

Practical steps:

1. Export customers and suppliers you trade with in the UK.
2. Flag records with no VAT number. Some will be genuinely non-VAT-registered (and may be out of scope; see non-VAT-registered businesses). Others are just incomplete.
3. Check each VAT number, starting with your highest-volume partners. Record the date of the check.
4. Compare the name and address returned with your record. Mismatches often reveal a trading name or a different group company.
5. Fix the record, or ask the partner to confirm.

Remember that a UK VAT invoice must show your own VAT number, and the customer's name and address (VAT Notice 700, section 16). Get your own details right first.

Northern Ireland and XI numbers

GOV.UK says a Northern Ireland business that has been recorded as operating under the Northern Ireland Protocol should use the XI prefix before its usual VAT number (for example XI 123456789 instead of GB 123456789) and must use it on documentation, such as invoices, when dealing with EU customers or suppliers. If you trade with such businesses, record both forms where relevant. How XI numbers will be handled in UK Peppol identifiers is not yet confirmed. See Northern Ireland and XI VAT and Peppol IDs in Northern Ireland.

Peppol IDs

A Peppol ID has two parts: a scheme code and a value. The OpenPeppol code list includes:

Scheme	Code	Notes
United Kingdom VAT number	9932	Active; country GB
Global Location Number (GLN)	0088	Active; international
D-U-N-S Number	0060	Active; international

Do not assume a partner uses its VAT number. Ask, or look it up in the Peppol Directory, and store the scheme and value as separate fields. See Peppol EAS codes for the UK and Peppol participant IDs.

Duplicates and group companies

• De-duplicate on VAT number first, then on company number and name.
• Where several group companies share a VAT group registration, keep separate records for each legal entity you contract with.
• Archive dormant records rather than deleting them, so history is kept for at least the six years HMRC generally expects for VAT records.

VAT code mapping

Build a table that maps every tax code in your system to a Peppol VAT category code and rate. Watch:

• reverse charge codes, for example construction;
• zero-rated versus exempt versus outside the scope;
• legacy codes that should be retired.

Unmapped or wrongly mapped codes are a common cause of validation errors.

Keep it clean

• Add VAT number checks and Peppol ID fields to new customer and supplier forms.
• Re-check VAT numbers for top partners periodically.
• Give one team ownership of master data.
• Report data-related invoice rejections monthly, and fix root causes.

What to do now

• Export in-scope customers and suppliers.
• Check VAT numbers for your top partners by volume.
• Fix your own entity details first.
• Build the VAT code mapping table.
• Add data clean-up to your project plan and readiness checklist.