I changed everyones tax codes at year end and the individual p9's that HMRC issue I applied too. One of the tax codes that I was given on the p9 has now suddenly changed from 747L to 66L.
I've just tried to contact HMRC but they are busy.
Thats what I thought had happened sorry but I've just been through all the records and I've found the problem. I have two p9's for the same person. The older p9 has 66L and the newer one 747L but I've overlooked the second one thinking it was a duplicate. I've rang sage and they said its ok just apply to new code from the next pay day and it will balance itself out. I will still contact HMRC to let them know. I really have no common sense :(