When you file a Capital Gains Tax return on a property disposal, HMRC's ability to enquire into that return does not expire quickly. Understanding how long records must be kept — and which documents matter most — protects you against unexpected questions years down the line.
How long can HMRC go back?
The enquiry window depends on the circumstances:
- Standard enquiry: HMRC has 12 months from the filing date to open a routine enquiry into a Self-Assessment return. For the 60-day CGT return, a similar window applies.
- Discovery assessment (careless error): If HMRC discovers an underpayment caused by a careless error, they can assess up to four years after the end of the relevant tax year.
- Discovery assessment (deliberate error): If HMRC believes the error was deliberate, the window extends to 20 years from the end of the tax year.
For most people, the relevant horizon is four years. But if there is any ambiguity about the correctness of a return — particularly around property valuations, PRR periods, or enhancement expenditure — the possibility of a later enquiry makes good records essential.
The most important documents to keep
Purchase documents
- Original completion statement (sets out the purchase price, SDLT, and solicitor's fees)
- SDLT confirmation from HMRC or your solicitor
- Surveyor's report (may establish condition at purchase, useful if there are subsequent capital improvement arguments)
- Conveyancing correspondence showing exchange date and completion date
Capital improvement records
This is the area most frequently challenged. Keep:
- Invoices from contractors for every capital improvement (extension, loft conversion, new kitchen/bathroom as genuine improvement, double glazing, etc.)
- Planning permission documents for significant works
- Building regulations completion certificates
- Photographs if possible (before/after improvements help establish the capital nature of the work)
The distinction between capital improvement and repair is important. Routine repairs and maintenance are not allowable for CGT. New roof replacing old — capital. Patching existing roof tiles — repair. New double glazing replacing single glazing — capital. Repairing a broken window — repair.
Occupation records (for PRR)
If Private Residence Relief applies because you lived in the property:
- Electoral roll registration records
- Utility bills showing the property as your address
- Bank statements and driving licence showing address
- Tenancy agreements showing start and end dates of lettings
- Evidence of occupation of any other property during periods you were not at this property
HMRC frequently challenges PRR periods, particularly where the ownership period is long and there were periods of absence or letting. Contemporaneous records of when you moved in and out are far more persuasive than estimates made years later.
Sale documents
- Completion statement from the sale
- Agency fees and advertising costs
- Legal fees on the sale
- Any other genuine costs of disposal
Digital records
HMRC accepts digital copies. Photographs of receipts stored in cloud storage, scanned completion statements, and PDF copies of correspondence are all acceptable. There is no requirement to keep original paper documents, though originals are preferable if available.
Organising records by property rather than by year is sensible — all the documents relating to a single property held together are much easier to retrieve when needed.
What happens if you cannot find the records
Missing documents are a genuine problem. If you cannot find the original completion statement from when you bought the property, options include:
- Asking your original conveyancing solicitor (they retain files for typically six years, sometimes longer)
- Checking your mortgage lender (they hold records for the duration of the mortgage)
- Land Registry — the transfer document is on the public register and shows the price paid
- HMRC's property transaction database may also hold details of the original purchase
Missing improvement records are harder to recover. HMRC does not have to accept an estimate. If invoices are lost, a surveyor's opinion on the cost of works may help, but it is not as strong as contemporaneous invoices.
After you file the 60-day return
Keep all the records used to prepare the 60-day return for at least four years from the end of the tax year of disposal. If there is any complexity in the calculation — disputed valuations, unusual PRR periods, deferred consideration — keep records for longer.
LetsFile retains a copy of the information used to prepare your return. If HMRC subsequently opens an enquiry, contact us — the Chartered Accountant/Chartered Tax Advisor who filed your return can assist with the response.