Even with the best payroll software, mistakes happen — a wrong tax code, a miscalculated overtime payment, an employee accidentally paid twice, or figures reported incorrectly to HMRC through Real Time Information. The good news is that HMRC has a well-established process for correcting payroll errors, and how you fix it depends mainly on when the mistake is discovered and whether it affected the employee’s pay, the figures reported to HMRC, or both.

Step 1: Identify Exactly What Went Wrong

Before correcting anything, pin down the specific nature of the error:

• Pay or deduction error: the employee was paid the wrong gross amount, or Income Tax/National Insurance was calculated incorrectly
• Reporting error: the employee was paid correctly, but the Full Payment Submission (FPS) sent to HMRC contained the wrong figures
• Payment date error: the wrong payment date was recorded, misaligned the payment with the incorrect tax period
• Employee information error: incorrect start or leaving dates, National Insurance category, or personal details

Compare the current period’s figures against year-to-date totals in your payroll software or submission log to confirm exactly where the discrepancy lies before making any correction.

Correcting the Figures Reported to HMRC

You cannot “reverse out” an FPS once it’s been submitted — instead, corrections are made by reporting the correct year-to-date figures going forward:

• If discovered within the same tax year: simply include the corrected year-to-date figures in your next regular FPS. There’s no need to resubmit each individual period separately; the correction flows through as an adjustment to the running total.
• If discovered shortly after the tax year ends (broadly, up to 19 April): you can generally still submit an additional FPS with corrected year-to-date figures as at 5 April for the previous tax year.
• If discovered later, after the final submission deadline has passed: a correction for an earlier tax year is generally still possible, but the process depends on your payroll software and how far back the correction relates — this is worth checking with your payroll provider or accountant, since the mechanism has changed in recent years and older correction methods (such as the Earlier Year Update) are being phased out for more recent tax years.

Correcting a payment date specifically follows a slightly different approach — an additional FPS with the correct payment date, marked with the appropriate late reporting reason, is generally the right route.

Will You Be Penalised for a Payroll Error?

Not automatically. HMRC has confirmed that a penalty only applies where the employer failed to take reasonable care or acted deliberately — a genuine, promptly corrected mistake generally doesn’t attract a penalty on its own. This is a similar principle to the behaviour-based penalty framework used elsewhere in the tax system, and it’s another reason to correct errors as soon as they’re identified rather than leaving them unaddressed.

If You Underpaid an Employee

Once the correct figures are established, the shortfall generally needs to be paid to the employee as soon as practicable, alongside the corrected PAYE reporting. Underpaying employees, even accidentally, can create separate employment law issues if it results in pay falling below the National Minimum or Living Wage for the hours worked, so it’s worth checking this specifically where an underpayment has occurred, not just correcting the PAYE figures.

If You Overpaid an Employee

Recovering an over-payment from an employee is more sensitive than it might first appear. While employers generally have the right to recover a genuine over-payment, doing so requires careful handling:

• Communicate clearly and promptly with the employee about the error and the proposed recovery
• Have a documented policy, or agree a reasonable repayment arrangement, particularly for larger amounts, rather than deducting the full sum from a single payslip without warning
• Be cautious about reducing a single deduction to the point where it takes pay below the National Minimum Wage for that pay period
• Keep clear records of the error, the amount, and how it was recovered, in case questions arise later

Unilaterally deducting a large over-payment without any communication can create genuine employment relations problems, even where the employer is technically entitled to recover the money.

Correcting Employer Payments to HMRC

A common misconception is that correcting an earlier period’s FPS changes what was owed to HMRC for that earlier period. In practice, corrections to previously reported figures typically adjust the payment due for the period in which the correction itself is submitted, not the original period — so if you correct a Month 3 error in Month 6, the adjustment generally shows up in your Month 6 liability to HMRC, rather than reopening the Month 3 payment.

What If HMRC’s Records Still Show the Wrong Figures?

If you’ve checked that the correct information was submitted via your RTI returns but HMRC’s own systems still show something different, this points to an error on HMRC’s end rather than in your submissions. In this situation, you can use HMRC’s dedicated service to query and correct an employer PAYE bill discrepancy, rather than resubmitting figures you’ve already confirmed are correct.

Preventing Payroll Errors Going Forward

A few habits significantly reduce the risk of recurring payroll errors:

• Reconciling payroll reports against bank payments each pay period, not just at year end
• Double-checking tax codes when HMRC issues updated notices, rather than assuming they’re correct
• Using payroll software that clearly flags year-to-date discrepancies before submission
• Reviewing new employee starter information carefully, since incorrect starter declarations are a common source of tax code errors

See our guide on small business payroll explained for a broader introduction to running payroll correctly from the outset.

How Felix Accountants Can Help

We help small employers correct payroll errors quickly and properly, handle the sensitive process of recovering over-payments from employees, and set up ongoing payroll processes that reduce the chance of errors recurring. Our payroll services can also take this off your hands entirely, running your payroll and managing HMRC reporting on your behalf.

Frequently Asked Questions

Can I fix a payroll error from an earlier pay period myself?

Yes, in most cases you correct it by including the updated year-to-date figures in your next regular FPS, rather than resubmitting the earlier period separately.

Will HMRC fine me for a genuine payroll mistake?

Not automatically. Penalties generally only apply where reasonable care wasn’t taken or the error was deliberate — a promptly corrected genuine mistake usually doesn’t attract a penalty.

Can I deduct an over-payment from an employee’s next payslip without telling them?

It’s strongly advisable not to. While employers generally have the right to recover a genuine over-payment, doing so without clear communication can create employment relations issues, and deductions shouldn’t reduce pay below the National Minimum Wage for that period.

Does correcting an old payroll error reopen what I owed HMRC for that earlier period?

Generally no. Corrections to earlier periods typically adjust the payment due for the period in which the correction is submitted, rather than reopening the original month or quarter’s liability.

What should I do if HMRC’s records don’t match what I submitted?

If you’ve confirmed the correct figures were submitted via RTI, this usually indicates an error on HMRC’s end, and you can use HMRC’s dedicated service to query and resolve the discrepancy.

There isn’t just one deadline for correcting a Self Assessment error — there are several, and which one applies depends on how the correction affects your tax bill, how long ago the return was filed, and whether HMRC has already noticed the issue themselves. Understanding these different time limits helps you work out exactly where you stand, and how urgently you need to act.

The Standard Amendment Window: 12 Months

For most straightforward corrections, you have 12 months from the original filing deadline to amend your return, whether online or on paper. For example, a 2024/25 return with a filing deadline of 31 January 2026 can be amended up until 31 January 2027. Within this window, corrections are relatively simple — log in to your HMRC online account (after a required 72-hour wait following the original submission), update the figures, and resubmit.

After 12 Months, But Within Four Years: Over-payment Relief

If you’ve missed the standard 12-month amendment window and the correction would mean you’d overpaid tax, you can make a formal claim for “over-payment relief.” This must generally be submitted within four years from the end of the tax year the return relates to, and requires a written claim to HMRC rather than a simple online amendment — including the tax year involved, the reason for the correction, the amount overpaid, and a signed declaration.

Underpayments Outside the 12-Month Window

If the correction means you owe more tax, rather than less, there isn’t a similarly generous window — you should notify HMRC as soon as you become aware of the error, regardless of how long ago the original return was filed. Voluntarily correcting an underpayment, even years later, is still treated far more favourably than waiting for HMRC to discover it independently, since it keeps the disclosure classed as unprompted for penalty purposes.

How Long Does HMRC Have to Challenge Your Return?

It’s worth understanding the position from HMRC’s side too, since it affects how long a genuine error could remain “live.” HMRC’s general time limits for opening a “discovery assessment” — essentially, going back and adjusting a previous year’s tax — depend on the reason for the inaccuracy:

• 4 years from the end of the relevant tax year, for genuine mistakes made despite taking reasonable care
• 6 years from the end of the relevant tax year, where the taxpayer failed to take reasonable care (a careless error)
• 20 years from the end of the relevant tax year, where the error was deliberate

Our guide on HMRC’s tax look-back periods covers this framework in more detail, and it’s the same underlying structure used to determine how many years landlords need to cover in a Let Property Campaign disclosure.

Why Acting Quickly Still Matters, Even Within a Longer Window

Even where you’re technically still within a four-year or longer window to correct something, waiting has real costs. Interest accrues on any underpaid tax from the original due date, regardless of when you get around to correcting it, so delaying simply increases the amount ultimately owed. There’s also a meaningful difference in how penalties are calculated between a genuinely prompt, voluntary correction and one that drags on for years before being addressed — our guide on prompted versus unprompted disclosures explains this distinction, and the same underlying principle applies to routine error correction, not just formal disclosure campaigns.

A Practical Summary of the Time Limits

What Happens If You Miss the Self Assessment Filing Deadline Entirely?

It’s worth distinguishing between correcting an error on a filed return and simply filing late in the first place. Missing the original Self Assessment deadline triggers its own automatic penalties, starting immediately after the deadline and increasing the longer the return remains outstanding. Our guide on HMRC’s penalties for missing the tax deadline covers this separate scenario, and our wider guide to key UK tax year dates and deadlines maps out the full annual calendar.

Special Cases: Multiple Years and Ongoing Income Sources

Where an error relates to an income source that’s been consistently under-reported across several years — such as rental income — each year technically has its own time limits, but it’s usually more practical to address them together through a structured process, rather than a series of separate corrections. This is exactly the situation the Let Property Campaign is designed for when the underlying issue is rental income specifically.

How Felix Accountants Can Help

We help clients work out exactly which correction route and time limit applies to their specific situation, whether that’s a straightforward in-year amendment, a formal over-payment relief claim, or a multi-year rental income disclosure. Our guide on HMRC compliance covers the wider penalty and behaviour framework that underpins all of this.

Frequently Asked Questions

What’s the deadline to amend a Self Assessment return online?

12 months from the original filing deadline. For example, a return with a 31 January 2026 deadline can be amended online until 31 January 2027.

Can I still get a refund if I missed the 12-month amendment window?

Yes, generally through a formal over-payment relief claim, which must be submitted within four years from the end of the relevant tax year.

Is there a deadline for telling HMRC I underpaid tax?

Not a fixed one in the same way — you should notify HMRC as soon as you become aware of an underpayment, regardless of how long ago the original return was filed, to keep the correction classed as voluntary.

How far back can HMRC go if they discover an error themselves?

Generally 4 years for a genuine mistake, 6 years for a careless error, and up to 20 years where the inaccuracy was deliberate.

Does correcting an old error always trigger a penalty?

Not necessarily. Genuine, voluntary corrections made with reasonable care are often treated leniently, and penalties depend heavily on the underlying behaviour rather than simply how long ago the error occurred.

Renovation work is where a lot of Let Property Campaign disclosures get genuinely complicated. Unlike straightforward running costs such as insurance or letting agent fees, renovation spending often sits in a grey area between “repair” (generally an allowable expense against rental income) and “capital improvement” (treated very differently for tax purposes). Getting this distinction right — and having the records to support it — makes a real difference to your disclosure.

Repairs vs Capital Improvements: The Core Distinction

This is the single most important distinction to understand before including renovation costs in a Let Property Campaign disclosure:

• Repairs and maintenance restore the property to its previous condition, or replace something on a “like for like” basis. Examples include fixing a broken boiler, repairing a leaking roof, or replacing a worn carpet with a similar one. These are generally deductible against rental income in the year the cost is incurred.
• Capital improvements go beyond restoring the property and instead enhance it, extend it, or add something that wasn’t there before — a loft conversion, an extension, or converting a single dwelling into two flats, for example. These aren’t deductible against rental income; instead, they’re generally added to the property’s cost base and only become relevant when calculating Capital Gains Tax on an eventual sale.

Why This Distinction Gets Genuinely Tricky

Many renovation projects mix both categories in a single job. Replacing a dated kitchen with a similar, modern equivalent is generally a repair; replacing that same kitchen while also knocking through a wall to create an open-plan layout introduces a capital element into the same project. Similarly, replacing single-glazed windows with double glazing has historically been accepted by HMRC as a repair, on the basis that double glazing is now the modern equivalent of a like-for-like replacement, even though it’s technically an improvement in performance.

This is exactly the kind of judgement call where professional advice earns its keep — getting the split wrong in either direction either understates a genuine deduction or overstates one, and both create problems in a disclosure.

What About a Property Bought in Poor Condition?

A particularly important rule to be aware of: if a property was purchased in a state of disrepair and renovation work was needed before it could be let at all, HMRC generally treats those costs as capital rather than revenue, even if the individual repairs would otherwise look like straightforward like-for-like work. This is because the cost of bringing a run-down property up to a let-table standard is seen as part of the acquisition cost, not an ongoing running expense of an already-established rental business. If your disclosure involves a property that needed significant work before its first tenancy began, this rule needs particular care.

Capital Allowances: A Separate Consideration

Certain capital expenditure — particularly on furniture, fixtures and equipment in furnished lettings, or on qualifying items in some commercial-adjacent scenarios — may separately qualify for capital allowances, which provide tax relief in a different way from either a straightforward repair deduction or Capital Gains Tax treatment. Our guide on maximising capital allowances for a property investor covers this in more detail, and it’s worth reviewing alongside any wider renovation spending.

What Records You’ll Need

Because the repair-versus-capital distinction depends heavily on the specific nature of the work, the quality of your records matters more here than almost anywhere else in a disclosure. Ideally, you’d retain:

• Itemised invoices from contractors, breaking down the work done rather than a single lump-sum figure
• Before-and-after photographs, which can help demonstrate whether work was genuinely like-for-like or represented a real change to the property
• Planning permission or building control records, where relevant, which often clearly indicate whether work went beyond a simple repair
• Dates of the work relative to the start of the letting, since per-letting renovation is treated differently from ongoing repairs during an established tenancy
• Bank statements or payment records confirming amounts paid and to whom

Our broader record keeping guide sets out what to retain across all categories of landlord expenditure, and our allowable expenses guide covers how different cost types are treated.

What If the Original Invoices Are a Single Lump Sum?

It’s common, particularly for older renovation work, to have only a single invoice covering a whole project without a breakdown between repair and capital elements. Where this happens, a reasonable, well-documented apportionment can be made — for example, based on quotes for comparable individual elements of the work, or a contractor’s recollection of the scope, clearly labelled as an estimate. This isn’t ideal, but it’s a workable and accepted approach where the original itemisation genuinely doesn’t exist.

How Renovation Costs Fit Into the Wider Disclosure

Renovation costs need to be allocated to the correct tax year — generally the year the cost was incurred, or in some cases spread differently depending on the nature of the work — and correctly categorised as repair or capital before they can be included in your Let Property Campaign calculation. Our guide on how many years you need to declare is a useful companion resource for understanding the overall disclosure period this fits within.

How Felix Accountants Can Help

Renovation costs are one of the areas we most commonly see get miscategorised in self-prepared disclosures — sometimes understating a genuine repair deduction, sometimes incorrectly claiming capital works against rental income. We review renovation spending line by line, apply the correct treatment, and help you build the record trail to support it, as part of our wider LPC disclosure guidance.

Frequently Asked Questions

Can I claim the cost of a new kitchen against my rental income?

Generally yes, if it’s a like-for-like replacement of an existing kitchen. If the work also involves structural changes, such as an extension or knocking through walls, that capital element isn’t deductible against rental income.

Are double glazing replacement windows a repair or a capital improvement?

HMRC has generally accepted replacing single glazing with double glazing as a repair, treating double glazing as the modern equivalent of the original, even though it’s technically an improvement.

Can I claim renovation costs incurred before my property was first let?

Generally no, if the property needed significant work to bring it up to a let-table standard before the rental business began — this is usually treated as a capital cost of acquisition rather than a revenue expense.

What if I don’t have itemised invoices for old renovation work?

A reasonable, documented apportionment between repair and capital elements can be used where original itemisation genuinely isn’t available, based on the best evidence available.

Do capital improvements ever reduce my tax bill?

Yes, but differently — capital improvement costs are generally added to the property’s cost base and reduce any Capital Gains Tax due when the property is eventually sold, rather than reducing rental income tax in the year the work was done.

Very few rental properties are let smoothly from 6 April to 5 April every single year. Tenants move out and there’s a void period before the next one moves in; a property is bought or sold partway through the year; a landlord moves in for a few months between tenancies. When you’re putting together a Let Property Campaign disclosure covering several tax years, working out exactly how much income and which expenses relate to each part-year period is one of the more fiddly calculations — but getting it right matters, since it directly affects how much tax is due for each year.

Why Part-Year Periods Come Up So Often in LPC Disclosures

Common reasons a property was only let for part of a tax year include:

• The property was purchased or sold partway through the tax year
• There was a void period between tenants, sometimes lasting several months
• The landlord lived in the property for part of the year before letting it out, or moved back in for a period
• The letting only began partway through the campaign’s relevant period, for example if the property was previously used differently

Each of these scenarios needs its own approach to correctly calculate the income and expenses that actually relate to the letting period, rather than the tax year as a whole.

Step 1: Establish the Exact Letting Dates

Before any calculation can begin, you need to pin down precisely when the letting period started and ended within each relevant tax year. This might come from tenancy agreements, a letting agent’s records, the completion date on a purchase or sale, or bank statements showing when rent first appeared. Where records are incomplete, a reasonable, clearly documented estimate is acceptable, provided the reasoning behind it is explained.

Step 2: Calculate Income for the Actual Letting Period Only

Only rent actually received (or due, if using the accruals basis) during the period the property was genuinely let should be included as rental income for that tax year. If a property was let from 1 October to 5 April in a particular tax year, only the rent relating to that six-month window counts as income for that year — not a full year’s worth of rent apportioned evenly, unless the actual rent received happens to align with that.

Step 3: Apportion Ongoing Costs Correctly

This is where part-year calculations get more technical. Some costs relate specifically to the letting activity and should only be claimed for the period the property was actually let or genuinely available to let; others are ongoing regardless of tenancy status and need a different treatment:

• Costs directly tied to the letting period: letting agent management fees, for example, generally only apply while a tenancy is active or the property is being actively marketed
• Costs that continue regardless of tenancy: mortgage interest, buildings insurance, and ground rent are often payable whether or not the property is currently tenanted, and can generally still be claimed for the full ownership period within the tax year, including reasonable void periods, as long as the property was genuinely held as part of a rental business rather than for personal use
• Costs relating to personal use periods: if the property was genuinely used as a personal residence for part of the year, expenses relating to that period generally can’t be claimed against rental income at all

Our detailed guides on property expenses and allowable expenses for property investors cover which costs fall into each category in more depth.

Void Periods: What Counts as “Still Let”?

A genuine void period — where the property is empty between tenants but still being actively marketed and available to let — is generally still treated as part of the rental business, meaning ongoing costs during that gap remain claimable. This is different from a period where the property was deliberately taken off the market, used personally, or left vacant with no active intention to re-let, which would generally break the continuity of the letting business for that portion of the year.

Worked Example

In this example, the full tax year’s ongoing costs would generally still be claimable, while rental income only reflects the two tenanted periods.

What If the Property Was Bought or Sold Partway Through the Year?

Where a property was purchased or sold during a tax year covered by the disclosure, only the period of actual ownership and letting is relevant — there’s no rental income or expense claim for the period before purchase or after sale. If the sale itself wasn’t reported separately, it’s also worth checking whether a Capital Gains Tax reporting obligation applies alongside the Let Property Campaign disclosure; our Capital Gains Tax guide covers this side of the picture.

Documenting Your Approach

Because part-year calculations involve a degree of judgement — particularly around whether a void period counts as ongoing letting activity — it’s important to document the reasoning behind each apportionment clearly. This protects the disclosure if HMRC has questions later, and shows a consistent, defensible methodology rather than figures that were simply estimated without explanation. Our record keeping guide sets out what’s worth retaining to support this.

How This Fits Into the Wider Look-Back Calculation

Part-year calculations need to be done separately for each tax year within your disclosure period, since the letting pattern often differs from year to year. Our guide on how many years you need to declare explains how the overall look-back period is determined, and each of those years will typically need its own careful income and expense calculation if the letting pattern wasn’t consistent throughout.

How Felix Accountants Can Help

Part-year and void-period calculations are one of the more common sources of error in self-prepared Let Property Campaign disclosures. We help landlords work through each relevant tax year methodically, correctly apportioning income and expenses, and documenting the approach so the disclosure holds up to scrutiny. See our guide to landlord accounting for the broader calculation framework this sits within.

Frequently Asked Questions

Do I need to claim expenses for the whole tax year if my property was empty for part of it?

Generally yes, for ongoing costs like mortgage interest and insurance, provided the property remained genuinely part of your rental business — for example, being actively marketed during a void period rather than taken off the market entirely.

How do I calculate rent for a property let for only part of a tax year?

Only the rent actually received or due during the genuine letting period counts as income for that tax year — it shouldn’t be averaged or apportioned evenly across the full year unless that happens to reflect the actual amounts received.

What if I can’t remember exactly when a tenancy started or ended?

A reasonable, documented estimate is acceptable where exact dates can’t be confirmed, based on the best available evidence such as bank statements or correspondence with a letting agent.

Does a void period break my entitlement to claim mortgage interest relief?

Not usually, as long as the property remained genuinely available and marketed for letting during that period, rather than being used personally or withdrawn from the rental market.

Do I need to do this calculation separately for every tax year in my disclosure?

Yes, since the letting pattern often varies year to year. Each tax year within your look-back period generally needs its own income and expense calculation reflecting what actually happened that year.