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HMRC compliance check letter: prepare your document upload pack
If HMRC asks for extra information during a compliance check, use the case reference and organise a clear, complete upload pack before sending anything.
Confirm that the upload service applies
HMRC’s GOV.UK service is for people who have received a letter from the compliance team asking for additional information. An authorised agent can send the information on the taxpayer’s behalf. Do not use this route simply because you want to volunteer unrelated documents or because a different HMRC team contacted you.
Read the letter first and copy its case reference exactly. The reference links the upload to the compliance check; an incorrect reference can delay the submission.
Build the pack around the request
Make a checklist from each item and period named in the letter. Preserve the original file names in a separate index, then record what each file proves, which period it covers and any gap you still need to explain. HMRC’s form accepts PDF, JPEG, XLSX, ODS, DOCX, ODT, PPTX and ODP files, with each file limited to 15MB and up to 10 files per upload.
Keep a copy of the submitted files and the date sent. If the requested evidence is unavailable, note what you tried to obtain and why; do not silently substitute an estimate for a document the letter specifically requests.
Submit and retain the confirmation
The service requires sign-in, allows progress to be saved and resumed, and sends a confirmation email with a submission reference after sending. Save that reference with the letter, your file index and any follow-up correspondence.
This workflow confirms delivery, not HMRC’s view of the tax position. Answer only the questions asked, keep explanations factual, and obtain professional advice if the request involves a dispute, suspected fraud, or material uncertainty.
Sources
- HM Revenue & Customs — Send documents or information to HMRC for a compliance check (2026-08-03)