Illness benefit not claimed - How much does employer take back?

My employer just wrote to me looking for illness benefit for back in oct/nov 2007. I didn't claim because the dates were 5 days or less and I thought this only applied for when you go over 5 days but it turns out its three. I know I probably should have asked at the time but the nature of the illness kind of made everything else go out the window. Anyhow I'm just wondering seeing as how they paid me full pay do they just take back the money they would have gotten from the illness benefit and how much would that be?
It breaks down like this
4 days
4 days
5 days

Does that mean I owe 13 days wages or 4 days taking into account that illness benefit isn't paid for the first 3 days of each period of illness?

Illness Benefit would not have been paid for the first three days of your first illness had you claimed. The 2 subsequent claims would have "linked" to the first claim and all days would have been paid. Therefore, you would have received 10 days Illness Benefit (13 less the first 3 days).

Thanks welfarite, is this the case even though i was back to work in between? first period was start october, then mid october then late november

Yes.

damn thats a lot of money to pay back then!

If you didn't make the claim did you not receive any money from Welfare? If that is so can you not just retrospectively cvlaim and give your employer any cheque you receive?

You can't make a backdated claim once 6 months have passed from the date of illness.