Ann in a case where someone owed Revenue say €5K and they were then made unemployed and unable to pay it is unlikely Revenue would chase the debt too vigorously....as long as you can prove that you don't have the funds to pay.
So the €5K would stand until such time as you are able to pay. Interest generally would not be added and Revenue would probably request an update on your circumstances i.e. have you found work after 12 months.
Each case is obviously different but I say the above from experience a few different cases.