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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 figures below are the maximum for each behaviour and the floor HMRC can reduce to, which depends on the quality of your disclosure (HMRC's Compliance Handbook, CH82470). Where a penalty actually lands within that band depends on how much you tell HMRC, how far you help, and how far you give access to records:
| Type of Error | Maximum Penalty | Minimum, unprompted disclosure | Minimum, prompted 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 a Schedule 24 penalty is a percentage of lost tax — so there is no penalty. You still have to correct the record.
A careless error disclosed before HMRC finds it has a minimum penalty of 0%, so an executor who comes forward promptly can end up owing the tax and interest but no penalty at all. HMRC does not publish figures for how often that happens, so we cannot tell you how common it is — only that the rule exists and that acting first is what triggers it.
If you discover you have made an error on your IHT return and you tell HMRC before they contact you (known as "unprompted disclosure"), the floor on the penalty falls. For a careless error, the minimum penalty with unprompted disclosure is 0%. For a deliberate error it is 20%, and for a deliberate and concealed one 30% — disclosure helps, but it does not wipe out a deliberate error.
If HMRC contacts you first (a "prompted disclosure"), the minimum penalty for a careless error rises to 15%, for a deliberate error to 35%, and for a deliberate and concealed one to 50%. The message is the same either way: the sooner you act, the lower the floor. 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.
HMRC refers property valuations it wants checked to the Valuation Office Agency's District Valuer, who has access to Land Registry sold prices. HMRC does not publish a tolerance — no percentage by which a valuation may be out before it is queried — so this guide does not state one. What protects you is being able to show how you reached the figure: a written valuation at the date of death, from someone qualified to give it. 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 helpline on 0300 123 1072 (Monday to Friday, 9am to 5pm) to discuss how to submit a correction before probate is granted.
Submit a C4 corrective account (see below), and note that this is not optional or open-ended: section 217 of the Inheritance Tax Act 1984 requires a further account within six months of the date you discover the defect. Do not distribute the estate before the corrective account has been accepted and any additional IHT paid. IHT interest accrues from the due date — the end of the sixth month after the month of death — so the sooner you correct the error, the less interest you will owe. The late-payment rate is 7.75% from 9 January 2026, but it tracks Bank Rate and moves, so check HMRC's current rate table.
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 delivered within six months of discovering the defect (Inheritance Tax Act 1984, s.217). It is signed by the executor or executors 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.
The C4 exists because adjustments during an administration are expected — assets valued more precisely, sales completing at different prices, omissions found while the estate is being wound up. HMRC does not publish how many it receives, so we cannot tell you how routine it is in numbers. What we can say is that delivering one is a statutory duty once you know the account was wrong, not a confession.
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.
Everything above about the probate application, the PA1P and PA1A forms and the Probate Registry describes England and Wales; Scotland has confirmation at the sheriff court and Northern Ireland its own probate office, each with their own forms. Inheritance tax, and everything on this page about HMRC, penalties and the C4, is UK-wide.
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.
The minimum penalty for a careless error disclosed before HMRC finds it is 0%, so a penalty is not inevitable. HMRC does not publish how often it applies one, so nobody can honestly tell you how likely it is in your case — what the rules do say is that the floor drops to nil only for an unprompted disclosure, and that the tax and the interest are still owed either way.
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.
Section 240 of the Inheritance Tax Act 1984 sets a limit on HMRC bringing proceedings to recover additional tax, rather than a window for opening an enquiry, and there are three periods, not two: 4 years ordinarily, 6 years where the loss of tax was brought about carelessly, and 20 years where it was brought about deliberately. Each runs from the later of the date the tax became due and the date the payment was made and accepted — not from the date you sent the account in. This is why keeping thorough records well beyond the end of the administration matters.
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.
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