Money Owed to Revenue

Hi I'm hoping someone can help me out on this one as I am really clueless when it comes to understanding tax unfortunately.

My boyfriend has a child that was born in sept 2005. He was told by solicitor that he could claim for one parent family credit as child stayed with him throughout the year.
He applied and received it for 2006 as was living with family at time and he moved in with me in september 2007 and applied for it again thinking that he would get the payment up until that month.
He never applied for 2005 as there was only 4 months from when child was born and didnt know about it at the time.

He got a letter today from revenue saying he owes €506 as they have offset the claim he never applied for in 2005 against the one he got in 2007(as he shouldnt have got it as was living with me for 4 months of that year).

If they have offset one year against another how can he owe money as was only living with me 4 months of that year and also son was born in sept 2005 which would also add up to 4 months? Is it due to the fact that he earned maybe €20 more a week in 2007?

We really cannot afford to pay this money at the minute as everything has gotten on top of us lately and we are already in debt the last few months so I'm really panicking and getting quite upset that this amount has to be paid in thirty days according to the letter.

Any advice in laymans terms would be great as I cant get onto revenue til tomorrow and am stressed out of my mind here.

TIA

As far as I know and I'm open to correction on this, but they probably won't take the 506 in a lump sum straightaway, they will more than likely spread it out over the course of the year.

I think Revenue have got that wrong. You are entitled to the One Parent Family Tax Credit if you have a dependent child resident with you for the whole or part of the year in question. I know it was allowable when I worked there several years ago. I'd go back to Revenue and get another opinion on this. If they still refuse then it won't be collected in one go, but spread out over the rest of the year.

Why don't you send a letter to the person in Revenue dealing with it and outline the history as you have done here and ask them to double check the calculations. Sometimes Revenue get their calculations wrong so they may have made a mistake in your case. It's always worth a try. But do it in writing and by registered post. In general anything revenue tells you over the phone or in person can not be relied upon.