Challenge Tax Underpayment

I received a P21 statement from Revenue which stated that I had underpaid tax by approx 4K for a previous year. The reason for this is due to an error on the part of Revenue.

The underpayment was caused at the time I switched jobs that year. A Tax Credit Certificate issued by Revenue to my new employer shortly after I started work, however this certificate did not include the previous earnings I had with my prior employer earlier that same year. My new employer calculated my tax liability for that year based on granting me full Standard Rate Cut off Point and full Tax Credits.

Given that the error was caused by the Revenue and not either by myself or my employer, do I have any grounds to challenge the tax underpayment finding?

Has anyone else come across a similar situation? Any advice would be greatly appreciated.

I accept that ultimately I am responsible to pay the proper amount of tax, however the amount is substantial and the circumstances were not of my creation.

This happened me... Revenue admitted error was theirs. Unfortunately the tax is still due. Mine was around 1200, so we agreed four years repayment. You can argue for a longer repayment term, particularly if repayment will leave you very short for a reasonable amount of net income. It definitely makes sense to keep an eye on your tax yourself to avoid this happening. Hopefully PAYE modernisation will remove this risk of error.

Short answer, no.

Your tax liability is a function of your income.

Unless some detail of your balancing statement is incorrect, ie the income or the amount of tax deducted, then you owe what you owe.

Agreed, you are still due to pay the tax. Least painful is to ask for your tax credits to be adjusted over 4 years.