according to the guardian it says;
"Those who are taxed through the pay-as-you-earn system would be asked to declare the benefit, putting them in a different tax code. The benefit would be recouped in the following tax year".
if it is that straight forward why not a code for higher earning single parents? that would solve the problem of a couple earning more but still getting it, the same goes for those who are not married but do co-habit. however, they point blank to refuse to solve this, they point blank don't care about equality and point blank don't care about how people live if it is 'not their way' [in other words and to use Cammerons words; "done the right thing"].
it is all rubbish. there is no saving incentive here, the cost of this will be huge. they are just trying to make us do what they want us to do/live like they want us to live.