Estate tax return deadlines for 2025 to 2026: register by 5 October 2026, paper SA900 by 31 October 2026, online filing and payment by 31 January 2027

An estate that has to be registered with HMRC for the tax year 2025 to 2026 must be registered by 5 October 2026. Its trust and estate tax return, form SA900, is due on paper by 31 October 2026 or online by 31 January 2027, and the tax is due by 31 January 2027.

Most estates never reach that point. This page works one that does.

Which estates have to register

GOV.UK gives three tests. An estate registers if any one applies:

• the value of the estate exceeds £2.5 million
• the value of assets sold by the personal representatives in any one tax year exceeds £500,000
• the total tax due exceeds £10,000

An estate that meets none of them, and has income over £500 in a tax year, pays under HMRC's informal arrangements by writing to HMRC. No SA900 is needed. An estate with no chargeable income and no chargeable gains does neither. The estate accounts guide works an estate of that kind, with the £500 rule.

The example estate

A retired teacher died on 12 August 2025.

The house sold at its probate value, so there is no gain to tax. The interest is over £500, so all of it is taxed. Personal representatives pay at the basic rate, which was 20% for 2025 to 2026:

£3,150 × 20% = £630.

Now the three tests.

The sale alone puts the estate into Self Assessment. Had the house fetched £480,000, a letter to HMRC and a payment of £630 would have settled the year.

The dates on this file

Registering on the last day leaves five days between the reference arriving and the paper deadline. The paper deadline is a Saturday and the January deadline a Sunday. A firm without the software is choosing between a paper return in October and buying software by January.

A tax agent registers through an agent services account. GOV.UK lists what is needed: the estate's name and address; each personal representative's name, address, date of birth and National Insurance or passport number; the name, last known address, date of birth, date of death and National Insurance number, if available, of the person who died; and the tax years in which tax is due. Registering does not give the firm authority to deal with HMRC for the personal representatives. That needs form 64-8.

What a late return costs

GOV.UK's penalties for a late return are:

• £100 at once
• after 3 months, £10 a day, up to £900
• after 6 months, 5% of the tax due or £300, whichever is greater
• after 12 months, another 5% or £300, whichever is greater

Late payment adds 5% of the unpaid tax at 30 days, 6 months and 12 months, with interest on top.

Suppose this return is filed and the £630 paid on 15 March 2027, six weeks late. The late filing penalty is £100. The tax was still unpaid 30 days after 31 January, which is 2 March 2027, so the late payment penalty is 5% of £630, or £31.50. That is £131.50 of penalties on a £630 bill, before interest.

Gains on the house

Had the house sold for more than its probate value, the gain would go on a Capital Gains Tax on UK Property return. HMRC's manual says a report is required on most sales of UK residential property within 60 days. GOV.UK says an estate has no chargeable gains to register for where they were reported that way. In this example the estate registers because of the sale proceeds and the taxable interest together: over £500,000 of assets sold, and income to report.

The year after

Interest earned from 6 April 2026 to the end of the administration belongs to 2026 to 2027. The £500 test is run again for that year. If this estate is still registered, that income goes on a second SA900, due on paper by 31 October 2027 or online by 31 January 2028.

A file note to copy

Estate of [name], died [date]. Tests for [tax year]: value at death £[amount] (over £2.5 million: yes / no). Assets sold in the year £[amount] (over £500,000: yes / no). Income tax and capital gains tax due £[amount] (over £10,000: yes / no). Result: register and file SA900 / informal arrangements / nothing to report. If registering: register by 5 October [year]; paper return by 31 October; online return and payment by 31 January [year]. Software held: yes / no. Checked by [solicitor] on [date].

Run the note at each 5 April while the file is open. The inheritance tax dates are separate and come earlier; the probate dates guide works them from the date of death.

A supervising solicitor reviews and signs anything a tool drafts, including a tax calculation or a return. This page is general information, not legal or tax advice.