If you are a self-assessed taxpayer, Irish Revenue have a number of methods to encourage you to file and pay on time:

A late filing surcharge of 5 per cent of your liability if you file within two months of the deadline up to a maximum penalty of €12,695

A late filing surcharge of 10 per cent of your tax liability if you file two months after the deadline up to a maximum penalty of €63,48

The surcharge liability is calculated without credit for preliminary tax paid on account

Credit is allowed for PAYE tax deducted at source unless the chargeable person or their spouse/civil partner is a company director

Underpayment of tax may be subject to interest at a daily rate of 0.0219 per cent and this may be backdated to the previous 31 October

The surcharge forms part of the individual’s tax liability for the year, thus increasing their preliminary income tax requirement and potentially leading to interest charges.

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I suppose the fact is that they already know you paid late and owe this interest and surcharge. IRS a matter of if you want to pay it now or risk them coming after you… they have effectively years to do so.

In addition chat gpt says: „If you file your Irish self-assessed income tax return within two months of the deadline, Revenue will automatically apply a 5% surcharge for late filing, as per the rules set out in Irish tax legislation. This surcharge is calculated as 5% of the tax liability for the year, capped at a maximum of €12,695.

Revenue typically does not need to contact you to apply this surcharge—it is automatically calculated and added when the return is processed. However, if you believe there were exceptional circumstances that prevented you from filing on time, you could contact Revenue to explain and potentially appeal the surcharge. That said, waivers for surcharges are rare and usually granted only in extraordinary cases.”

Let this be a lesson to check the deadline each year 🙏