I don't know if this has been brought up before but I am getting myself in a tizz about the 2012/13 reductions for Child Tax Credit and I think i have found the formula for working it out.
I will first say if this is wrong I am sorry.
But the formula seems to be:
Take your combined/single income and then for anything over then minus the threshold of 15,860 then times by 41p.
Then add the family element 545.00 and then the child element of 2,690 for each child (also add any severe or sever disabled child element if applicable)
then take off from this anything from the disregard income and this should be your yearly award
An example is:
If a couple earned £22,000 a year then take off the £15,860 threshold leaves £6140.00 then times this by 41p equals £2,517.00.
Then add family element plus child element for 2 children so £545.00 plus £5,380 this makes £5,925.
Then take the £5,925 and take off the £2,517.00 and this leaves your tax credit award for the year of £3,408.00.
I have not done the workings out for Working Tax credit as I am not entitled to this so basically not interested.
Hope this helps.