Electronic Invoices (e-Invoicing) vs. Paper Invoices in the UK

HMRC Accepts Electronic Invoices

PDF invoices sent via email are fully legal and compliant with HMRC. You don't need to print and post them. Digital is the norm now.

Types of Electronic Invoices

• PDF email — Most common. Send PDF attachment via email. Fully valid.
• EDI/API — Automated system-to-system transmission. Used by large corporates.
• Portal — Customer logs in to view invoice. Must allow download as PDF for records.
• Email (unencrypted text) — Not recommended. Hard to authenticate and store securely.

Legal Requirements for Electronic Invoices

• Authenticity — Customer can verify it came from you
• Integrity — Invoice hasn't been altered after sending
• Legibility — Customer can read and print it
• Storage — You can store it securely for 6 years

Paper Invoices: Still Legal

You can still issue printed invoices if you prefer:

• Post to customer
• Hand-deliver
• File as original for your records

But there's no advantage. Digital is faster, cheaper, and better for the environment.

Best Practices for Electronic Invoices

• Email subject line — "Invoice INV-0045 from [Your Company]" (clear and searchable)
• File naming — "INV-0045_ABC_Ltd_15May2026.pdf" (includes invoice number, customer, date)
• Attachment — PDF only (never editable Word docs)
• Secure storage — Keep copy in cloud (Google Drive, OneDrive, Dropbox) or accounting software
• Digital signature (optional) — Adds extra authenticity, but not required for UK invoices

Common Mistakes

• Sending as Word doc (customer can edit it)
• Sending as email body text (no attachment, can't be stored properly)
• Not keeping copies
• Deleting old emails thinking you've deleted the invoice (you haven't — they have a copy)

FAQ

Is email PDF as legal as a posted invoice?

Yes, fully. HMRC accepts email-sent PDFs with no distinction.

Do I need digital signatures?

No. Standard PDF sent via email is sufficient. Digital signatures add extra verification but aren't required for UK invoices.

What about encrypted email?

Fine if the customer requests it (e.g., for confidentiality). Doesn't affect HMRC compliance.