This explanation taken from
here (end of page) may help explain it further:
Time limits/Statute of Limitations
There are time limits (limitation periods) for taking most types of court action. These time limits are set either in the
Statute of Limitations 1957, as amended, or in specific legislation dealing with the court issue involved.
The law in relation to time limits is complex but, in general, the time limit for taking actions for breach of contract (for example, failure to pay for goods or services provided), for debt judgments and for non-payment of charges such as rent is 6 years. This means that if your creditor does not start the court action within 6 years of the debt being due, the action is
statute-barred. Effectively, that means that you cannot be forced to pay the debt.
If your creditor gets a judgment, then, in general, they have 12 years in which to
enforce that judgment.
The general rules do not apply to taxes. There is a 4-year time limit on the Revenue Commissioners seeking tax from you and there is a 4-year time limit on you seeking repayment of taxes that you were not due to pay. However, if there is any fraud or neglect, there is no time limit.