If you are self-employed you must file an annual tax return. If you fail to do so on time – or at all – you may be subject to interest, fines and penalties. Interest can be chargeable at up to 8% per annum. Where a tax
return is submitted less than two months after 31
October, there is a 5% surcharge, up to a maximum of €12,695. If returns are still outstanding after this date, a higher surcharge of 10% of the tax liability will apply.

Ensure you pay the correct amount of preliminary tax to ensure you do not pay interest.