Capital Gains Tax on a UK property sale: the 60-day report-and-pay deadline and a completion diary table

A client completes the sale of a buy-to-let on a Friday and asks: "Is that everything, then?" For the conveyancing file it may be, but the tax may not be. GOV.UK sets a short window to report and pay Capital Gains Tax on most UK property sales, and the window can close while the file is already in the archive.

What the GOV.UK page says

As summarised from the page on 29 October 2026:

• The deadline. "You must report and pay any Capital Gains Tax on most sales of UK property within 60 days."
• Whose sales. The page is aimed at property that is not the seller's own home: buy-to-let, business premises, land and inherited property.
• Estates. For property belonging to the estate of someone who has died, the page says the information goes in when reporting the estate to HMRC.
• Gifts. The page says gifts to a husband, wife, civil partner or charity generally need no payment.

The page as I read it did not say when the 60 days start. Search-engine summaries from accountancy sites say completion, not exchange, but those are not a primary source, so check the start date on the HMRC guidance before relying on it. The table below counts from completion as a working assumption.

The 60-day diary table

The arithmetic is calendar days from the completion date, then calendar days from 29 October 2026 to that last day.

Checks. From 1 September, 29 days reach 30 September and 60 reach 31 October; 29 October to 31 October is 2. From 15 September, 15 days reach 30 September, 46 reach 31 October and 60 reach 14 November; 2 (to 31 Oct) + 14 = 16. From 1 October, 30 days reach 31 October and 60 reach 30 November; 2 + 30 = 32. From 29 October, 2 days reach 31 October, 32 reach 30 November and 60 reach 28 December. The 14-day column is a diary rule for a firm to set, not a legal one; 60 minus 14 leaves 46 days in hand.

The first row is the point of the table: a sale completed on 1 September has two days left today, and the client may not have been told.

Where this meets the conveyancing file

• Ask at instruction. Is the property the client's home, or let, inherited or held as an investment? Add that line to the client care letter checklist, and say in writing that tax advice is or is not part of the retainer.
• Diary on completion day. Put 60 days in the diary when the completion statement goes out. The residential purchase checklist shows where the sale side sits in the matter.
• Estate sales. If the seller is an estate, the page points to the estate return route; the estate tax return deadlines and the inherited house gain worked example cover that side.
• Say who files. If the firm does not report the gain, the closing letter should say that the client, or their accountant, must.

What I did not read

I did not read the HMRC guidance on how to work out the gain, the start of the 60 days, penalties and interest for late reporting, the position of non-UK residents, or the exceptions for no tax due. Check each with a primary source before you advise.

Overlyft builds AI staff who join your firm's team, read the completion date from the file, work out the last reporting day and draft the diary entry and the closing-letter line, with a person approving each one.

This is general information, not legal advice. Check the current legislation and your own obligations for each client.