Reviewed by: MyTaxRebate Team on 10 Mar 2026 | Authority: s.472 TCA 1997
Quick Answer
Incorrect PAYE deductions on your salary occur when your employer deducts more income tax than Revenue's credit certificate requires, or when Revenue's certificate itself contains incorrect credits or rate band information. Under s.112 TCA 1997, your employer is obliged to deduct PAYE tax based on Revenue's instructions - but those instructions can be wrong if your tax credit information was not correctly registered with Revenue. The Employee Tax Credit (s.472 TCA 1997, €1,875 in 2025) and Personal Tax Credit (€1,875 in 2025) must both be applied against your liability - if either was missing from your certificate, your employer over-deducted tax throughout the year. Emergency tax is the most visible form of incorrect deduction, but errors in credit allocation, rate band assignment, and relief claims also result in overpayments that must be actively recovered from Revenue.
What This Page Covers
- ✓The most common causes of incorrect PAYE deductions
- ✓How to identify incorrect deductions on your payslip
- ✓What the difference between emergency tax and a credit error looks like
- ✓How to recover incorrectly deducted tax from Revenue
- ✓How MyTaxRebate identifies and corrects payroll errors on your behalf
Key Facts at a Glance
- ✓Emergency tax (40% flat deduction) is the most visible and significant form of incorrect PAYE deduction.
- ✓Credit allocation errors - where Revenue's certificate does not include all credits you are entitled to - cause systematic under-deduction each pay period.
- ✓Standard rate band errors - where your €42,000 at 20% is not correctly allocated - cause higher-rate deductions on income that should attract the lower rate.
- ✓Incorrect deductions from prior years are recoverable for up to four years - 2022, 2023, 2024, and 2025.
- ✓Your employer cannot refund prior-period overpayments - these must be claimed from Revenue directly.
- ✓MyTaxRebate reviews payroll records across all claimable years to identify every instance of incorrect deduction.
- ✓Backdate up to four tax years - in 2025, PAYE refunds are claimable for 2022, 2023, 2024, and 2025.
Most Common Causes of Incorrect Deductions
Emergency tax. When you start a new job without your PPS number and previous employment details being registered with Revenue before your first pay date, your employer applies a flat 40% deduction on all income. This continues until Revenue issues a correct tax credit certificate. The 40% rate applies regardless of your actual tax rate - even if all your income is within the standard rate band, you pay 40% rather than 20% during the emergency tax period. Every pay period on emergency tax generates an incorrect deduction equal to the difference between the 40% charged and your actual rate, plus any credits that were not applied.
Credit omissions. Revenue issues your tax credit certificate to your employer, specifying your credits and standard rate band. If the certificate does not include credits you are actually entitled to - for example, if your marital status change was not updated with Revenue, or if a qualifying credit was not applied - your employer deducts tax based on the lower (incomplete) credit figure. This is technically a Revenue error, not an employer error. The missing credits must be claimed through a refund submission.
Week 1 / Month 1 basis. In addition to emergency tax, Revenue can instruct your employer to apply your credits on a non-cumulative "Week 1" or "Month 1" basis - meaning only the current period's credit allocation is applied, not the cumulative entitlement for the full year to date. This typically occurs where Revenue is still processing a change (new job, returned from abroad, reactivated employment). While it results in the correct rate, it prevents any credit catch-up from earlier months - meaning if you earned more in earlier months, those months' unused credits cannot be applied. A year-end refund claim corrects this.
How to Spot Incorrect Deductions on Your Payslip
Your payslip does not tell you if the deduction was correct - it only shows what was deducted. However, there are indicators to look for: if your PAYE deduction seems disproportionately high relative to your gross pay, if you can see a "Week 1" or "Month 1" notation, or if you recall receiving less net pay than expected when starting a new role, these are indicators that a deduction may have been higher than necessary. A rough check: multiply your monthly gross salary by 20% and subtract one-twelfth of your €3,750 annual credits. If your actual monthly PAYE deduction significantly exceeds this, something may be wrong.
Check Your Claim
MyTaxRebate can review your position and guide the next step.
How to Identify an Incorrect Deduction
The most reliable way to verify whether your employer deducted the correct amount is to compare your payslip deductions against your tax credit certificate and apply Revenue's rate band to your actual income. If the credit shown on your certificate is €3,750 (standard credits for a single person) but the deductions on your payslips indicate that only a portion of that credit was applied, the difference is an overpayment. Similarly, if you were on emergency tax (flat 40% deduction) for any pay period, the payslip will show a higher deduction than your credit certificate rate. Revenue's your Revenue record shows your credit certificate for each year, allowing a direct comparison.
Recovering Incorrect Deductions from Prior Years
Whether an incorrect deduction arose from a credit certificate error, emergency tax, or a payroll administrative mistake, the recovery process is the same: submit a backdated PAYE refund claim for each affected year within the four-year window. Revenue reviews the claim against PMOD payroll data, recalculates the correct liability, and refunds the difference. Revenue does not penalise claimants for recovering overpayments that resulted from employer or administrative errors. MyTaxRebate identifies all incorrect deduction periods across the four claimable years and includes them in a single consolidated claim.
The Time Limit for Correcting Incorrect Deductions
Incorrect tax deductions from prior years can be corrected through a backdated refund claim, subject to Revenue's four-year time limit. In 2025, claims can be submitted for 2022, 2023, 2024, and 2025. The 2022 tax year closes permanently on 31 December 2026 - after that date, any incorrect deduction from 2022 cannot be recovered. If you believe incorrect tax was deducted in any year since 2022 - whether from emergency tax, a credit certificate error, or a payroll mistake - a review now ensures the entitlement is captured before the window closes.
Check Your Claim
MyTaxRebate can review your position and guide the next step.
Tax Scenarios
Emergency tax - new employer, 10 weeks
An engineer joined a new company in February 2024 on emergency tax for ten weeks. His monthly salary was €4,500. At 40% emergency tax, monthly deductions were approximately €1,800 vs his correct liability of around €590 (after credits applied at standard rate). The monthly overpayment was €1,210, and over ten weeks his total incorrect deduction was €2,790. After correcting for mid-year adjustment, the recoverable amount was €1,960 - confirmed and paid by Revenue within four weeks.
Week 1 basis - cumulative credits not applied
A returning emigrant who restarted PAYE employment in Ireland in March 2023 was placed on Week 1 basis by Revenue for the first five months while her status was being processed. Because cumulative credits were not applied, she missed €780 in credit carry-forward from January and February. MyTaxRebate identified this from the payroll records and submitted a 2023 refund claim for €780, which Revenue confirmed without an information request.
Missing credit on certificate
A widowed father qualified for the Widowed or Surviving Civil Partner Credit but had never registered it with Revenue. His credit certificate therefore omitted this credit, causing a systematic overdeduction of tax each year. MyTaxRebate registered the credit with Revenue and submitted backdated claims for all four years. The combined four-year refund from the previously unclaimed credit was €2,880.
Common Mistakes To Avoid
- ✗Assuming your employer will correct prior-period errors: Employers apply corrections prospectively from the date of the new certificate. They cannot refund prior-period overpayments - that must come from Revenue via a claim.
- ✗Not checking if all your credits are on the certificate: Revenue issues credits based on what it knows about you. If you have had a life change (marriage, separation, widowhood, qualifying child) and did not update Revenue, credits may be missing from your certificate.
- ✗Ignoring Week 1/Month 1 notations on your payslip: Week 1 basis means cumulative credits are not being applied - this is a sign that a year-end refund claim may be needed to correct the position.
- ✗Not claiming prior years: Incorrect deductions from recurring credit errors recur year after year. All four claimable years should be reviewed together for a complete recovery.
When This Does Not Apply
Key Takeaways
- ➤ Emergency tax is the most common and significant form of incorrect PAYE deduction - fully recoverable for up to four years.
- ➤ Credit omissions on Revenue's certificate cause systematic overdeduction that accumulates every pay period.
- ➤ Your employer cannot refund prior-period overpayments - recovery must come from Revenue via a formal claim.
- ➤ Week 1/Month 1 basis on your payslip is a sign that a year-end refund claim is likely needed.
- ➤ MyTaxRebate identifies and claims all forms of incorrect deduction across all four claimable years.
Check Your Claim
MyTaxRebate can review your position and guide the next step.
Frequently Asked Questions
What is the difference between emergency tax and a credit error?
Emergency tax is a specific Revenue instruction to deduct at a flat 40% when no credit certificate is in place. A credit error occurs when a certificate is in place but contains incorrect or incomplete credit information. Emergency tax typically applies at the start of employment before any certificate is issued. A credit error can persist throughout an entire year if the wrong credits are on the certificate. Both result in incorrect deductions and both are recoverable through a refund claim.
Can I correct a credit error myself through your Revenue record?
You can update certain credit information through Revenue's your Revenue record system, and this will prompt Revenue to issue an updated certificate to your employer. However, updating going forward does not automatically refund prior-year overpayments. For backdated recovery of incorrect deductions, a formal refund claim covering each affected year is required. MyTaxRebate handles this full process on your behalf.
How do I know if my tax credit certificate was incorrect?
The most reliable way to check is to compare the credits on your certificate against your actual entitlements. Revenue lists the credits you receive on the certificate issued at the start of each year. If you have had a life change (marriage, divorce, a qualifying child, change in home carer status, qualifying disability) and did not notify Revenue, a credit may be missing. MyTaxRebate checks your full credit entitlement against your actual credits at the time of reviewing your refund claim.
My employer says the tax was correct - can it still be wrong?
Your employer is correct in saying they applied Revenue's instructions correctly. The issue is whether Revenue's instructions themselves were correct. If the tax credit certificate issued by Revenue to your employer contained incorrect or incomplete information, the deductions were technically "correct per the certificate" but incorrect relative to your actual legal entitlement. The recovery comes from Revenue, not from your employer.
How far back can I claim for incorrect tax deductions?
Revenue's statutory time limit allows claims for up to four years from the end of the relevant tax year. In 2025, that means incorrect deductions from 2022, 2023, 2024, and 2025 are all recoverable. The 2022 window closes permanently on 31 December 2026. Where the same credit error affected multiple years, all of those years should be included in a single consolidated claim.
