Payment due date, IHT400 deadline and HMRC late payment interest, worked out day by day.
| Interest period | Rate | Days | Interest |
|---|
Estimate only, check with HMRC. Uses HMRC late payment interest rates checked October 2026 (simple interest, 365 day year). It does not work out how much Inheritance Tax is owed.
This inheritance tax deadline calculator is for executors and administrators of estates in the UK: enter the date of death and it gives the Inheritance Tax payment due date, the IHT400 account deadline and the HMRC interest on anything paid late. It uses the HMRC late payment interest rates day by day, so a rate change in the middle of a delay is charged correctly. Figures checked October 2026.
Quick answer: Inheritance Tax must be paid by the end of the sixth month after the month of death, so a death on 14 January 2026 means payment by 31 July 2026. The inheritance tax deadline calculator then adds HMRC simple interest from the next day, at 7.75% a year since 9 January 2026.
In This Guide
What Is the Inheritance Tax Payment Deadline?
The Inheritance Tax payment deadline is the last day of the sixth month after the month in which the person died. It is not six months from the date of death, which is a common mistake: a death on 1 March and a death on 31 March both have a due date of 30 September.
Interest is simple, not compound. In plain words: interest = unpaid tax × annual rate × days late ÷ 365, with each day charged at the rate HMRC set for that day. Since 6 April 2025 the late payment rate has been Bank Rate plus 4 percentage points, up from Bank Rate plus 2.5 before then, which is why older articles quoting 7.25% or less are now out of date.
| Month of death | Inheritance Tax due by | IHT400 account due by |
|---|---|---|
| January 2026 | 31 July 2026 | 31 January 2027 |
| April 2026 | 31 October 2026 | 30 April 2027 |
| July 2026 | 31 January 2027 | 31 July 2027 |
| October 2026 | 30 April 2027 | 31 October 2027 |
How Much Interest Does HMRC Charge on Late Inheritance Tax?
HMRC charges 7.75% a year on late Inheritance Tax from 9 January 2026, which works out at about £21.23 a day on every £100,000 unpaid. The rate follows Bank Rate, so it moves several times in a typical estate.
Take James, executor for his mother, who died on 14 January 2026. The estate owes £120,000. He paid £20,000 from her bank account through the Direct Payment Scheme before the 31 July 2026 deadline, but the house sale only completes on 30 November 2026. The £100,000 balance is 122 days late, so the interest is £100,000 × 7.75% × 122 ÷ 365 = £2,590.41, and he must send £102,590.41 in total. Every extra week the sale slips adds about £148.63.
How to Use the Inheritance Tax Deadline Calculator
Step 1: Enter the Date of Death
Use the date on the death certificate. The tool shows the payment due date and the IHT400 deadline straight away, which is useful even before you know how much tax is owed.
Step 2: Enter the Tax Due and Any Payment
Type the Inheritance Tax figure from your IHT400 calculation and anything already paid by the due date. Only the unpaid balance attracts interest, so paying part of the bill early from the deceased's bank or building society account cuts the cost.
Step 3: Choose the Payment Date and Rate
Pick the date you expect to pay the balance. Keep the HMRC rate table for real figures, or switch to your own rate if HMRC announces a change after October 2026. The days between dates calculator is handy for checking the number of days late on a statement. Tick the box to see a 10 year instalment plan.
Step 4: Read the Deadlines and Interest
The inheritance tax deadline calculator then shows the interest, the total to send, the daily cost of further delay and a table of each rate period used, so you can compare your figure with the HMRC statement line by line.
Can You Pay Inheritance Tax in Instalments?
Yes, tax on things that take time to sell, such as a house, a controlling shareholding or a business, can be paid in 10 equal yearly instalments. The first is due on the normal deadline and the rest fall on each anniversary. Under the GOV.UK instalment rules interest is added to later instalments on the outstanding balance, and the whole balance becomes payable if the asset is sold. For assets inherited from 6 April 2026 that qualify for Agricultural Relief or Business Relief, no interest is charged on the balance as long as each instalment is paid on time.
What Happens If the IHT400 Is Sent Late?
A late IHT400 account can bring a fixed £100 penalty, a further £100 if it is 6 months or more late, and up to £3,000 if it is more than 12 months late. The HMRC Inheritance Tax Manual says the penalty is capped at the tax due, and a reasonable excuse can cancel it. If the empty family home is costing you more while it sits unsold, the council tax empty homes premium calculator shows when an empty property premium could start.
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How we checked this tool: the Tools Veria Editorial Team built this tool by hand, checked it against the official rules or published standards where they apply, and tested it against worked examples. Results are estimates for planning, not personal financial or tax advice. Read our editorial policy and disclaimer, or report an error.
Frequently Asked Questions
When do you have to pay inheritance tax?
By the end of the sixth month after the month of death. For example, a death on 14 January 2026 gives a due date of 31 July 2026. Interest starts the day after.
What is the HMRC interest rate on late inheritance tax?
It is 7.75% a year from 9 January 2026, which is Bank Rate plus 4 percentage points. Interest is simple, charged daily on the unpaid tax until the day it is paid.
Do you have to pay inheritance tax before probate?
Usually some of it, yes. You normally need to pay at least part of the tax before HMRC will let the grant of probate go ahead, often from the deceased's bank accounts through the Direct Payment Scheme.
How long do you have to send the IHT400 form?
The IHT400 account is due within 12 months of the end of the month of death. A death in January 2026 means sending it by 31 January 2027, even if the tax was paid earlier.
Is interest charged on inheritance tax instalments?
Not on the first instalment if paid on time. Later instalments carry interest on the outstanding balance, except for assets inherited from 6 April 2026 that qualify for Agricultural Relief or Business Relief.
Can HMRC waive interest on late inheritance tax?
No. Interest is not a penalty, so it is charged even when the delay is not your fault, such as a slow house sale. Paying part of the tax early is the only way to reduce it.