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Mistakes on a probate application are more common than most executors realise — and the consequences vary enormously depending on what type of mistake it is and how you handle it. A typo on the PA1P form is easily corrected. An undeclared gift that reduces the IHT bill is a different matter. This guide explains what to expect, what to do, and how HMRC's penalty regime works. For a broader overview, see our guide to common probate mistakes executors make.
Probate mistakes fall into two broad categories: administrative errors on the PA1P or PA1A application form, and substantive errors on the IHT return (the IHT400, or no IHT return at all for qualifying excepted estates).
The PA1P (where a will exists) and PA1A (where there is no will) ask for basic information: the deceased's full legal name, date of birth, date of death, last address, details of the will, and the executor's own particulars. Common errors include:
If the Probate Registry spots an inconsistency — for example, a name that does not match the will exactly — they will write to you requesting a correction or a sworn statement explaining the discrepancy. This is routine. It delays the grant but does not result in penalties.
If the error is discovered only after the grant is issued, you can apply for a revised grant. This is more time-consuming but equally not a financial or legal disaster. See our guide to completing the PA1P and PA1A probate application forms for guidance on getting it right first time.
Errors on the inheritance tax return are treated separately from probate registry errors and fall under HMRC's jurisdiction. These range from the minor (a forgotten Premium Bond account worth £100) to the significant (an undeclared gift of £50,000 or an undervalued property).
HMRC distinguishes between three types of error for penalty purposes:
For a detailed explanation of how HMRC investigates estates, see our guide on what to do when you receive an HMRC IHT compliance check letter.
Under Schedule 24 of the Finance Act 2007, HMRC can charge penalties for inaccuracies in IHT returns. The maximum penalties are:
| Type of Error | Maximum Penalty | With Unprompted Disclosure |
|---|---|---|
| Careless error | 30% of lost tax | 0–15% |
| Deliberate error | 70% of lost tax | 20–35% |
| Deliberate and concealed | 100% of lost tax | 30–50% |
"Lost tax" means the difference between the IHT HMRC should have received and what was actually paid. If the estate was below the nil-rate band regardless of the error, there is no lost tax and therefore no financial penalty — though HMRC may still issue a non-financial penalty notice.
The vast majority of executors who make honest mistakes face no penalty at all — provided they come forward promptly when they discover the error. HMRC is generally reasonable with genuine mistakes. Penalties are reserved for those who are careless to an egregious degree, or who act deliberately.
If you discover you have made an error on your IHT return and you tell HMRC beforethey contact you (known as "unprompted disclosure"), penalties are dramatically reduced. For a careless error, the minimum penalty with unprompted disclosure is 0% — HMRC effectively waives the penalty entirely for an executor who comes forward honestly and promptly.
If HMRC contacts you first (a "prompted disclosure"), the minimum penalty for a careless error rises to 15%. This is still modest, but the message is clear: the sooner you act, the better. See our guide on how to respond to an HMRC probate query for practical steps.
Not all IHT errors are equal. Here is a rough guide to the seriousness of common mistakes:
Forgetting a small building society account, a Premium Bond holding, or a minor investment worth a few hundred pounds is extremely common and generally treated with great leniency by HMRC. If the additional assets do not push the estate over the nil-rate band, there is no additional IHT due and therefore no penalty at all — you simply need to submit a corrective account to complete the record. See our guide on what to do if you've missed an asset in probate.
Valuing a share portfolio or an investment account incorrectly is more significant, but provided the error was genuinely made in good faith (for example, using an outdated share price), HMRC will generally accept a correction without penalty. The key is to use reasonable methods to value each asset and to keep records of how you arrived at your figures.
Property is the most common source of significant IHT disputes. HMRC uses the District Valuer Service and Land Registry comparable data to check property valuations. An undervaluation of 10–15% may be accepted as within the normal range of valuation uncertainty; larger discrepancies attract close scrutiny. See our guide on what happens if you give the wrong property value for probate.
Omitting gifts from the 7 years before death is one of the most serious types of IHT error, because HMRC may view it as deliberate concealment if the gifts were large and obvious. If you are the executor and you knew about the gifts but did not declare them, HMRC can treat this as a deliberate error. See our guide on declaring gifts for probate and IHT.
The steps to take depend on whether the grant has been issued yet.
Contact HMCTS Probate Registry immediately. If the error is on the PA1P form, you can usually submit a corrected version. If the error is on the IHT400, contact HMRC's Inheritance Tax department on 0300 123 1072 to discuss how to submit a correction before probate is granted.
Submit a C4 corrective account (see below). Do not distribute the estate before the corrective account has been accepted and any additional IHT paid. Also note that IHT interest accrues from the due date (normally 6 months after the end of the month of death), so the sooner you correct the error, the less interest you will owe.
For background on IHT interest and how it accrues, see our guide to probate delays and IHT interest.
The C4 is HMRC's official form for correcting an IHT400 after it has been submitted. You use it to:
The C4 must be signed by the executor(s) and sent to HMRC Inheritance Tax (not to the Probate Registry). HMRC will calculate any additional tax and interest due and send a revised computation. Once agreed, you pay the balance owed.
The C4 is available to download from GOV.UK. If you are using the corrective account to reduce the IHT bill (for example, because you overvalued a property and it has since been sold at a lower price), HMRC will arrange a repayment.
Submitting a C4 corrective account does not automatically trigger an investigation. HMRC processes thousands of corrective accounts every year. It is the normal, expected mechanism for handling the inevitable adjustments that arise during estate administration — assets valued more precisely, sales completing at different prices, or omissions discovered during the course of administering the estate.
Yes, in certain circumstances. Executors take on personal liability in two situations:
For a detailed explanation of executor liability, see our guide to executor personal liability in the UK.
It is worth distinguishing between errors that affect the IHT calculation and errors in the administration of the estate itself. For example, distributing assets in the wrong proportions, or paying a debt that should not have been paid from the estate, are administration errors. These may give rise to claims from beneficiaries but are handled differently from HMRC IHT errors.
For the full picture of things that can go wrong during probate, see our guide to probate mistakes executors make in the UK and our estate administration checklist.
Prevention is far less stressful than correction. The most effective steps are:
They will write to you (or your solicitor) asking for clarification or a corrected form. The grant will not be issued until the issue is resolved. This is routine and happens frequently — it is not an investigation or a sanction.
Not if you correct it promptly. HMRC's penalty policy for careless errors with unprompted disclosure starts at 0%. For genuinely honest mistakes disclosed before HMRC asks, penalties are rarely applied in practice. The key is acting promptly once you discover the error.
No — you can submit a C4 corrective account yourself. HMRC provides guidance notes with the form. However, if the error is large (for example, a significant property undervaluation being queried by HMRC), it may be worth taking professional advice before responding. See our guide to dealing with HMRC querying a property valuation.
HMRC has 4 years from the date the IHT account was delivered to open an enquiry for innocent or careless errors. For deliberate errors, they have 20 years. This is one reason why keeping thorough records for several years after probate is completed is so important.
Submit the C4 corrective account to HMRC to correct the IHT position. Pay any additional IHT and interest due. If there is no money left in the estate, you may need to recover funds from beneficiaries who received a larger share than they were entitled to. This is legally possible but practically difficult — it is a strong reason to avoid early distribution. See our full guide on what to do if you missed an asset in probate.
What triggers HMRC to investigate an inheritance tax return, how to present your IHT400 to minimise scrutiny, and why property valuation and gift declaration are the most important factors.
Which gifts must be declared on IHT403, the 7-year rule, potentially exempt transfers, gift with reservation of benefit, annual exemptions, and how to find gifts in the estate records.
What to do if you discover a missed asset during or after probate — how to submit a C4 corrective account, IHT interest implications, and what happens if the estate has already been distributed.
What happens if HMRC challenges your property valuation for probate. How the District Valuer Service works, how to negotiate, IHT and interest implications, and how to correct an error via the C4.
When executors face personal liability. Distributing before paying debts, Section 27 Gazette notices, and when to consider an executor's bond.
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