DIRT is your only liability if you have other income that allows for a DIRT credit to be created.
PAYE Income: 50,000 EUR
Deposit Interest: 1,000 EUR
Step 1) DIRT paid: 270 EUR to the bank automatically.
Step 2) Declare 1,000 EUR deposit interest.
Step 3) Revenue charge you 27% tax on your deposit interest AND at the same time grant you a tax credit for 270 EUR. The tax credit was only issue because you had PAYE/other income to cover this tax credit.
Hence, you do not pay anything further that you original DIRT payment to the bank because of other income that allowed for the creation of a DIRT tax credit.