Interesting tax avoidance strategy?

[oyster]

By using pension AVCs or pension salary sacrifice, we know that one can reduce one's 'effective' salary to a lower level to take advantage of lower tax rates, child benefit etc.

But can it also be used more extremely to earn working and child tax credits?


Let's say I made enough of a pension salary sacrifice so that my effective salary was only £15k, could I claim the benefits?


I'm seeing the problem as being the need to have the earnings assessment based on the previous year. Not sure if child tax credits and working tax credits can be claimed retrospectively via a self assessment tax return.