Invoicing a government department: e-invoicing rules

Government departments have been legally required to accept compliant e-invoices since 18 April 2019. If you hold a public contract, you can send a structured invoice that meets EN 16931, and the department must process it if it is undisputed. From April 2029, the obligation flips: VAT invoices to public bodies must be sent as e-invoices.

What the law says today

For contracts procured under the Procurement Act 2023 (from 24 February 2025), section 67 implies a term into every public contract:

the contracting authority must accept and process for payment any electronic invoice … which is in the required electronic form, and not disputed by the authority.

"Required electronic form" means compliant with BS EN 16931-1:2017 and using a syntax listed in PD CEN/TS 16931-2:2017: UBL or UN/CEFACT CII. A PDF attachment does not qualify. The Act defines an e-invoice as one in "a structured electronic format that allows for its automatic and electronic processing".

Older contracts carry the same obligation under regulation 113A of the Public Contracts Regulations 2015. It was inserted by the 2019 regulations and applied to central government authorities from 18 April 2019.

Departments can choose the channel

Section 67(6) lets an authority require a particular system for e-invoices. That is why some departments direct suppliers to a specific portal or shared-service provider. The Act expressly allows defence authorities to require a system that charges suppliers fees. No other authority is given that permission.

Cabinet Office guidance adds that parties can agree other invoicing methods, such as paper, but suppliers "will always have the right to submit an electronic invoice".

Defence and security

Under the Defence and Security Public Contracts Regulations 2011 (as amended in 2019), the e-invoicing term did not apply where a contract was classified secret or needed special security measures, and the UK's essential security interests could not otherwise be protected. The Security Service, the Secret Intelligence Service and GCHQ are excluded from the Procurement Act altogether (section 2(5)).

Payment: 30 days, and published performance

Section 68 implies payment within 30 days of the invoice being received, or by the invoice's due date if that is later. The term does not apply while the authority considers the invoice invalid or disputes it, but it must tell you without undue delay.

Points worth knowing:

• Valid invoice. An invoice is valid if it is a compliant e-invoice, or if it sets out your name, a description of what you supplied, the sum requested and a unique identification number, and meets any other contract requirements.
• When the clock starts. If the contract names an e-invoicing system, receipt is when the invoice reaches that system.
• Supply chain finance cannot be used to cut what you are paid within the 30 days, according to the guidance.
• Published performance. Section 69 requires authorities to publish payments compliance notices on their performance against the 30-day term. legislation.gov.uk shows it brought into force in stages during 2026.

If you are a subcontractor

Section 73 pushes the 30-day payment terms down the supply chain into public sub-contracts. However, the rule that a compliant e-invoice is automatically valid (s.68(8)(a)) does not apply to sub-contracts. A prime contractor is not bound by the Act to accept your e-invoice, although from 2029 the VAT mandate will cover B2B invoices anyway.

Devolved governments

Body	Regime
UK government departments (including in Scotland, Wales and NI for reserved matters)	Procurement Act 2023
Welsh Government and its bodies	Procurement Act 2023, with Welsh Government guidance
Northern Ireland departments	Procurement Act 2023 (some provisions, such as section 69, do not apply to transferred NI authorities)
Scottish Government and devolved Scottish bodies	Public Contracts (Scotland) Regulations 2015, regulation 70A

Scotland's regulation 70A has implied an e-invoice acceptance term into Scottish central government contracts since 18 April 2019.

What April 2029 changes for government suppliers

Confirmed:

• VAT invoices issued to public-sector bodies must be e-invoices from April 2029.
• The government has announced that Peppol will be the core interoperability network for UK e-invoicing.
• The model is decentralised: invoices go supplier to buyer through service providers, with no government clearance platform and no real-time reporting at launch.

Not yet confirmed:

• Whether departments' existing portals will remain acceptable once the mandate starts, or will need to connect to Peppol
• Whether section 67's definition of "required electronic form" will be changed (Ministers have a power to do so under s.67(7), after consultation)
• The UK invoice specification, including whether it will be Peppol BIS Billing 3.0 as is or a UK CIUS
• How government's own Peppol identifiers will be published and maintained

Expect more detail in the roadmap due at Budget 2026 on 28 October 2026.

Practical checklist for suppliers

• Find out how each department customer receives invoices now: Peppol, portal or email.
• Put the PO number and any buyer reference exactly where requested. Missing references are the most common reason invoices stall.
• Use the contracting entity named on the contract, not a parent department.
• Keep evidence of the date each invoice was received. With a structured e-invoice, your Access Point or portal log gives you this.
• Ask your software provider about its Peppol plans. See choosing an Access Point.
• If you are a prime contractor, plan how you will receive e-invoices from your own subcontractors by 2029.

What to do now

If you already have a public contract, you can use your right to e-invoice today. It shortens disputes and gives you a clear receipt date. Getting onto Peppol now also prepares you for every B2B customer in 2029. Read the council guide, the NHS guide and the mandate overview.