Applying taper to child tax credit?

tyllwyd

Our family income has gone up this year , and I'm trying to work out whether it is going to be worthwhile bothering to give the tax credits people details of our income, or whether just to tell them that we don't want to claim from now on. It's a bit more complicated for me because I'm self-employed, so of course I don't have figures to hand yet for 2007-08.

Does anyone know what your joint income has to be for the child tax credit to be reduced to zero?

For the tax credit that they are paying now (April 2008 onwards) - is this based on your income for the previous year (2007-08) or the year before that (2006-07)?

At the moment, they are paying us tax credit but I'm pretty sure that in this tax year (2008-09) we are going to earn too much and won't be entitled to anything. Does that mean that the tax credit they are paying now will be OK because it is based on the previous year's earnings, or are they going to ask for anything paid from April 08 back? (I've got no problem paying it back, it's just that I'd rather not get it in the first place if I'm not entitled to it, to save complications!)