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Advanced Taxation (UK) · Capital gains tax: the use of exemptions and reliefs in deferring and minimising tax liabilities

CGT Administration, Interest and Payment Deadlines

Updated 11 October 2026 · Fact-checked

CGT is reported and paid either within 60 days of completion for UK residential property where tax is due, or through the self-assessment return and 31 January payment for other disposals. Interest on late tax is 8.50% a year and on overpaid tax 3.50%, using the rates in the ACCA tax tables.

Understand CGT Administration, Interest and Payment Deadlines

CGT is a tax on the gain, not on the sale price. Once you have worked out the gain, the next question is when HMRC must be told and when the money must be paid. ATX-UK often asks this as a short part of a bigger planning or advice question.

There are two routes. For a disposal of UK residential property on which CGT is payable, the individual must make a return and pay the tax within 60 days of completion. This is separate from the normal tax return. If no CGT is due, for example because the gain is fully covered by private residence relief, losses or the annual exempt amount, no 60-day return is needed.

For all other disposals, such as shares or business assets, the gain goes on the self-assessment return for the tax year of disposal. The return is due by 31 January after the end of the tax year if filed online. The CGT is normally paid by the same 31 January date. A disposal in 2025/26 is therefore reported and paid by 31 January 2027.

If tax is paid late, interest runs from the due date until the date of payment. If tax is overpaid, HMRC pays interest to the taxpayer. The ACCA tax tables give assumed rates: 8.50% on underpaid tax and 3.50% on overpaid tax. The 3.75% official rate in the same table is for beneficial loans, not for late tax.

Separately, penalties can apply for late filing, late payment and errors. For errors in a return, the table of standard penalties gives a maximum and a minimum that depends on behaviour and on whether disclosure was prompted or unprompted. In the exam, write the deadline, the amount, the interest and any penalty range, and tie each to the facts given.

Key rules to remember

UK residential property CGT
Report and pay within 60 days of completion
Applies where CGT is payable on a UK residential property disposal. No 60-day return if no tax is due.
Other disposals
Return and payment by 31 January following the end of the tax year
Example: disposal in 2025/26 gives a 31 January 2027 deadline for online filing and payment.
Interest on underpaid tax
Tax unpaid × 8.50% × months late ÷ 12
Rate from the ACCA tax tables. Interest runs from the due date. Apportion to the nearest month.
Interest on overpaid tax
Tax overpaid × 3.50% × months ÷ 12
Rate from the ACCA tax tables. This is interest paid to the taxpayer.
CGT rates and annual exempt amount
Lower rate 18%, higher rate 24%, annual exempt amount £3,000
Use the rates in the tables. Gains within the unused basic rate band are taxed at 18%, the rest at 24%.
Standard penalties for errors
Careless: max 30%, min 0% unprompted, 15% prompted. Deliberate not concealed: max 70%, min 20% unprompted, 35% prompted. Deliberate and concealed: max 100%, min 30% unprompted, 50% prompted
Applied to the extra tax due as a result of the error.

How to solve CGT Administration, Interest and Payment Deadlines questions

Use this method for any question on CGT reporting, payment or interest.

  1. 1Identify the asset. Is it UK residential property, or something else such as shares or a business asset?
  2. 2Fix the date of disposal. For property, this is the completion date. For other assets, work out the tax year it falls in.
  3. 3Compute the CGT first if the amount is needed. Deduct losses and the £3,000 annual exempt amount, then apply 18% or 24% according to the basic rate band available.
  4. 4State the deadline. For residential property with tax due, it is 60 days after completion. Otherwise it is 31 January after the end of the tax year.
  5. 5If payment is late or early, count the months from the due date to the payment date, rounding to the nearest month.
  6. 6Compute interest as tax × rate × months ÷ 12. Use 8.50% for underpaid tax and 3.50% for overpaid tax.
  7. 7If there is an error or late filing, state the penalty range from the table, matching the behaviour and whether disclosure was prompted.
  8. 8Finish with a clear sentence of advice to the client, tied to the facts.

Quickest way: Deadline, amount, months, rate

When to use it: Use when the question gives you a disposal date and asks when to pay or what interest is due.

  1. Write the asset type next to the date. This sets the deadline route.
  2. Write the deadline date straight away. Count 60 days for residential property, or find the 31 January for other assets.
  3. Write the tax figure. Reuse any CGT already computed.
  4. Find the months late and multiply: tax × 8.50% × months ÷ 12.
  5. Add one line on penalties if the question mentions errors or late filing.

Common mistakes in CGT Administration, Interest and Payment Deadlines

  • Applying the 31 January deadline to a UK residential property sale where tax is due.

    Students remember the self-assessment date and apply it to every disposal.

    Fix: Check the asset first. Residential property with CGT payable needs a return and payment within 60 days of completion.

  • Counting the 60 days from the contract date.

    Contract and completion dates are both given in the scenario.

    Fix: Use the completion date as the start of the 60 days.

  • Using the 3.75% official rate for interest on late CGT.

    It appears in the same table as the interest rates.

    Fix: The official rate is for beneficial loans. Use 8.50% for underpaid tax and 3.50% for overpaid tax.

  • Charging interest on the whole gain instead of the unpaid tax.

    Students rush and take the first number they see.

    Fix: Interest is calculated on the tax unpaid, after losses, the annual exempt amount and the rate bands.

  • Working in exact days or leaving the months unrounded.

    Students want to be precise.

    Fix: The supplementary instructions say apportionments are to the nearest month, so work in whole months.

  • Quoting only the maximum penalty.

    Students recall one figure from the table.

    Fix: Give the range. The minimum depends on whether disclosure was prompted or unprompted, so identify the behaviour and the disclosure type.

Worked examples

Example 1

Ravi is a higher rate taxpayer. He sold a UK residential rental property, completion on 10 August 2025, with a gain of £60,000 before the annual exempt amount. He has no losses. He paid the CGT on 31 January 2026. State the filing and payment deadline, compute the CGT, and compute the interest, rounded to the nearest £.

Show the solution
  1. Deadline: UK residential property with tax due, so the return and payment are due within 60 days of completion.
  2. Count from 10 August 2025. There are 21 days to 31 August, a further 30 to 30 September (51 days), and 9 more days gives 9 October 2025.
  3. CGT: £60,000 less the £3,000 annual exempt amount gives £57,000.
  4. As Ravi is a higher rate taxpayer, the gain is taxed at 24%. £57,000 × 24% = £13,680.
  5. Late payment: from 9 October 2025 to 31 January 2026 is about 3¾ months, which is 4 months to the nearest month.
  6. Interest: £13,680 × 8.50% × 4 ÷ 12 = £387.60, which is £388.

Answer: The deadline is 9 October 2025. The CGT is £13,680 and the interest on the late payment is £388.

Example 2

Meera, a higher rate taxpayer, sold quoted shares in September 2025 for a gain of £23,000 and has no losses. She did not report the gain. In July 2027 she told HMRC and paid the tax on 31 July 2027, after the original due date. Her failure was careless and the disclosure was unprompted. State the original due date, the CGT, the interest, and the penalty range.

Show the solution
  1. Due date: shares are not UK residential property, so the gain belongs on the 2025/26 return. Online filing and payment are both due by 31 January 2027.
  2. CGT: £23,000 less £3,000 annual exempt amount gives £20,000. At 24% the tax is £4,800.
  3. Interest: from 31 January 2027 to 31 July 2027 is 6 months. £4,800 × 8.50% × 6 ÷ 12 = £204.
  4. Penalty: the behaviour is careless. The maximum is 30% of £4,800 = £1,440.
  5. With unprompted disclosure the minimum is 0%, so the penalty can be reduced to nil, with a range of £0 to £1,440.

Answer: The CGT of £4,800 was due on 31 January 2027. Interest is £204. The penalty range is £0 to £1,440 because the careless error was disclosed unprompted. The same facts with prompted disclosure would give a minimum of 15%, or £720.

Exam tips

  • Always say which route applies. Write 'UK residential property, so 60 days from completion' or 'other asset, so 31 January' before any figures.
  • Show the interest working in one line: tax × 8.50% × months ÷ 12. Even if the tax figure is wrong, you can still collect method marks.
  • Round months to the nearest whole month, as the supplementary instructions require, and say that you have done so.
  • Use the table of standard penalties by matching the behaviour first, then the disclosure type. Give both ends of the range.
  • In advice questions, add one practical point, such as paying the CGT on time to avoid interest or telling HMRC promptly to reduce penalties.

Practice questions from Capital gains tax: the use of exemptions and reliefs in deferring and minimising tax liabilities

CGT Administration, Interest and Payment Deadlines in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

CGT Administration, Interest and Payment Deadlines: frequently asked questions

What is the CGT payment deadline for residential property in ATX-UK?

Where CGT is payable on a UK residential property disposal, you report and pay within 60 days of completion. If no CGT is due, no 60-day return is needed. Other disposals follow the normal self-assessment timetable.

What interest rate applies to late CGT in the ATX-UK exam?

Use 8.50% a year on underpaid tax and 3.50% a year on overpaid tax, as shown in the ACCA tax tables. Do not use the 3.75% official rate, which is for beneficial loans. Interest runs from the due date.

When is CGT on shares due?

The gain is reported on the self-assessment return for the tax year of disposal, and the CGT is normally due by 31 January after the end of that tax year. A disposal in 2025/26 is due by 31 January 2027.

Are penalties for CGT errors in the tax tables?

Yes. The standard penalties for errors give a maximum and a minimum penalty by behaviour: careless, deliberate but not concealed, and deliberate and concealed. The minimum depends on whether the disclosure was prompted or unprompted.