CGT Record Keeping for Property Sales: What to Save and How Long to Keep It

The records you keep are not box-ticking. They are the difference between paying capital gains tax on the real gain and paying it on the sale price because you could not prove what the property cost you. When you sell a rental property, every pound of base cost, every qualifying improvement and every cost of sale has to be evidenced, and the burden of proof sits with you, not with HMRC.

This guide sets out what to keep across the life of the property, the retention period that actually applies (which is not the six years most sites quote for personal landlords), how Making Tax Digital reshapes the form your records take, and how to rebuild a base cost when the paperwork has gone missing.

How long must you keep CGT records for property?

The legal hook is section 12B of the Taxes Management Act 1970. Because letting property is treated as a business for record-keeping purposes (the Salisbury House Estate principle), the longer business-records rule applies, not the 22-month rule that covers a straightforward employee.

That longer rule is widely misquoted as "six years". For a personal landlord it is not. The income tax and CGT floor is five years after the 31 January following the tax year of disposal. The six-year figure is the corporation tax period for companies. Selling through a company, or as an individual, changes the number.

Who is selling	Statutory minimum (s.12B)	Worked example: sale in 2026/27
Individual landlord (income tax and CGT)	5 years after 31 January following the tax year	Keep until at least 31 January 2033
Company (corporation tax)	6 years from the end of the accounting period	6 years from the company's period end
Any seller where HMRC opens an enquiry	Until the enquiry is closed (plus an appeal window)	Can run well beyond the floor
Our standing recommendation	7 years	Buffer against late-discovered errors

Two practical points follow. First, never destroy the original purchase paperwork while you still own the property, whatever the retention clock says, because the base cost is fixed at acquisition and you may not sell for decades. Second, if you file a return late, the clock runs from the date you actually filed, not the original deadline, so a late filer keeps records longer.

What documents you need for property CGT calculations

Your file should capture everything that moves the three numbers in a CGT calculation: what the property cost you (base cost), what you spent improving it (enhancement expenditure), and what it cost you to sell (disposal costs). The table below is the reference set.

Stage	Documents to keep	Why it matters for the gain
Acquisition	Completion statement, SDLT/LBTT/LTT return and payment, conveyancing invoice, survey or valuation, probate valuation for inherited property	Fixes the base cost deducted from the sale proceeds
Improvement	Builder and trade invoices, planning consents and building-regulation approvals, architect and surveyor fees, before-and-after photos	Capital improvements reduce the gain; routine repairs do not
Disposal	Sale completion statement, estate agent commission invoice, sale conveyancing invoice, EPC, marketing costs	Costs of sale are deducted from proceeds

Acquisition and purchase documentation

The completion statement is the single most important document you will ever hold for the property, because it is the primary evidence of what you paid. Keep it with the conveyancer's invoice (legal fees and searches are part of the base cost), the Stamp Duty Land Tax return and payment evidence (or the Land and Buildings Transaction Tax return in Scotland, or the Land Transaction Tax return in Wales), and any survey or valuation. For an inherited property the probate valuation sets your base cost in place of a purchase price, so it is non-negotiable.

Enhancement and improvement records

This is where most landlords lose money at sale, because the line between an improvement and a repair is poorly understood. An improvement creates something that was not there before or materially upgrades the asset: an extension, a loft conversion, a first central-heating system, a new bathroom where there was none. A repair restores what was already there: replacing a worn boiler, redecorating, re-roofing on a like-for-like basis. Only improvement still reflected in the property at sale reduces the gain. Repairs are revenue costs, deductible against rental income instead. Keep the invoices detailed enough to show which is which, and photograph the work, because a faded receipt for "building works, £14,000" with no detail is the kind of figure HMRC challenges.

Disposal and sale documentation

On sale, the completion statement again carries the headline figure, this time the proceeds. Keep the estate agent's commission invoice and the conveyancing invoice for the sale, both of which are deductible disposal costs, along with any marketing spend and the Energy Performance Certificate. Small disposal costs add up, and they come straight off the gain.

Can you store CGT property records digitally?

Yes, and for many landlords you will soon have no choice. HMRC accepts digital copies as long as they are complete and legible, and landlords within Making Tax Digital for Income Tax are required to keep their records digitally. A workable system has clear scans or photos, two backups in different places (cloud plus a local copy), a folder per property broken down by tax year, and reasonable protection on sensitive financial documents. Keep irreplaceable originals such as completion statements physically secure as well, because a corrupt file is not a defence.

How Making Tax Digital changes your record keeping

Making Tax Digital for Income Tax is no longer on the horizon, it is live and phasing in by income level: from 6 April 2026 for landlords whose qualifying income exceeds £50,000, from 6 April 2027 above £30,000, and from 6 April 2028 above £20,000. Joint owners test the threshold against their own share of gross property income, not the property's total. In scope, you keep digital records and submit quarterly updates through compatible software.

Two things landlords routinely get wrong here. The digital-records requirement changes the form of your records, not how long you keep them: the s.12B retention period is untouched. And MTD covers your rental income reporting, not the CGT side. The records you assemble for an eventual sale sit alongside your MTD records, they are not replaced by them. Our guide to MTD record keeping for landlords covers the digital obligations in full.

Special situations that extend record keeping

Some circumstances push the retention period beyond the statutory floor or demand a thicker file than usual.

HMRC enquiries and investigations

If HMRC opens an enquiry into a return, you must keep all relevant records until that enquiry is closed, plus a sensible window for any appeal. For a contested property valuation or a complex disposal this can add years. This is the practical reason we recommend seven years rather than the bare statutory minimum.

Connected-party transactions

Sales between connected parties (family members, business partners, related companies) are treated as taking place at market value regardless of what actually changed hands, so HMRC scrutinises them closely. Keep evidence of how you arrived at the market value used, ideally an independent valuation contemporaneous with the transfer.

Spouse and civil partner transfers

A transfer to a spouse or civil partner is no-gain-no-loss under s.58 TCGA 1992, which means the receiving spouse takes over your original base cost and acquisition date. The implication for record keeping is easy to miss: the receiving spouse needs your full acquisition and improvement file, not just the transfer paperwork, because their future gain is calculated from your original cost. Our guide to CGT on property transfers between spouses works through the mechanics.

Private Residence Relief claims

If you are claiming Private Residence Relief on a property that was at times your main home and at times let, the relief is apportioned by time. It is therefore only as strong as the occupancy dates you can prove. Keep council tax bills, utility accounts, electoral-roll evidence and the tenancy agreements that mark the let periods.

Rental income records versus CGT records

The two systems overlap but answer different questions. Rental income records (rent received, allowable expenses, repairs) feed your annual return and follow the same five-year floor. CGT records can span the entire ownership period, because the base cost is locked in at purchase and only the gain is tested at sale. Some documents do both jobs: a major improvement invoice is enhancement expenditure for CGT and, where part of the work is genuinely a repair, an allowable cost against rental income. Holding everything in one property file rather than two parallel systems removes the risk of a document being filed under "rental" and lost by the time you sell.

Reporting and paying after a sale

Records do not exist in a vacuum, they exist to support what you report. Where capital gains tax is due on a UK residential disposal, you must file the UK property CGT return and pay the tax within 60 days of completion, then report the same disposal again on your Self Assessment return for the year. Where the gain is fully covered by Private Residence Relief, losses or the £3,000 annual exempt amount, a UK resident does not need to file the 60-day return, but a non-UK resident must report every UK land disposal regardless of whether tax is due. Residential gains for 2026/27 are charged at 18% (basic rate) and 24% (higher rate), and the annual exempt amount is £3,000.

The records carry directly into both filings. A clean file lets you file the 60-day return on time, which matters because late filing attracts a £100 fixed penalty, daily penalties from day 91, and tax-geared penalties at six and twelve months. For the full timeline see our guide to CGT payment deadlines for property sales, and for the calculation itself see how to calculate CGT on a buy-to-let sale.

Record keeping for different ownership types

Buy-to-let, commercial and development property

A standard residential buy-to-let needs the full acquisition, improvement and disposal file above, with particular care on improvement spend. Commercial investors should also keep records of any capital allowances claimed, because allowances interact with the CGT calculation. For development projects, keep every cost (land, construction, professional fees, finance) because the documentation often decides whether the profit is taxed as a trade (income tax) or as a capital gain.

Incorporation and business changes

Transferring a portfolio into a company is itself a disposal for CGT, so it demands a market value for each property at the transfer date and, if you are relying on it, evidence to support an incorporation relief claim. The acquisition file you have kept for each property feeds straight into that calculation. If incorporation is on your radar, start with our guide to the buy-to-let limited company, and remember that once inside a company the retention rule shifts to the six-year corporation tax period.

What happens if records are lost or incomplete?

A missing file is a problem, not a disaster. You can usually rebuild the key figures from independent sources:

• Land Registry records show the purchase price and date
• Your conveyancer's file is typically retained for six to seven years after completion and may hold the completion statement
• Mortgage lender records can evidence the loan and arrangement costs
• Old bank statements can show payments to builders and professionals
• HMRC's own records may confirm the SDLT return and payment

Where the figure cannot be fully reconstructed, HMRC may accept a reasonable estimate supported by what evidence you do have. But the burden of proof is yours, so the more contemporaneous documents you can assemble, the closer the agreed figure will be to the truth rather than to HMRC's cautious assumption.

Getting the file right before you sell

The cheapest time to organise CGT records is years before the sale, when documents are still obtainable and memories are fresh. A short annual review at the same time you do your tax return catches gaps while they can still be filled. If your records are scattered, or you are weighing a sale, a transfer or incorporation, a specialist property accountant can pressure-test the file before HMRC does and make sure no allowable deduction is left on the table. For the wider picture on disposals, see our complete guide to capital gains tax on property in the UK.