Remember everyone, when you're calculating how much worse off you'll be under the proposed TC changes, you need to note that NMW will increase from £6.50 to £7.20 and the income tax threshold is also increasing.
So for example someone who works 30 hours p/w at NMW and with a child:
NMW will rise to £7.20 from next April, therefore gross income will rise from £10,200 (ish) to £11,300 (ish). With the income tax threshold increase, they will pay the same tax as they currently pay. Thus, in terms of income they will be approx. £1100 better off.
Tax credit changes come into effect at the same time: Under 2015-16 the deduction from the maximum is £1549.80. Under 2016-17 with the new withdrawal limit and taper the deduction would be £3048, thus in terms of Tax Credits alone they will be £1498 worse off
So, once the Income Tax and Tax Credit changes are taken into account, this family would be around £398 worse off per year.
Anyone earning over the Income Tax threshold will not see as much of a dip in their disposable income as those who earn under the threshold, and those earning NMW will also see less of a dip.