There is no easy way for Osborne to cut the £30 billion tax credit bill

How do you solve a £4.4 billion hole like tax credits?

At 12.30pm on Wednesday, we'll find out.

Front and centre of this combined Autumn Statement and Spending Review will be George Osborne's plan to solve his tax credit headache.

He announced the cuts in July, angered many of his own MPs and then suffered an embarrassing defeat in the House of Lords.

So after being ordered by peers to soften the impact of the tax credit cuts, the Chancellor won't be able to save the same amount of money on the same timescale.

He could raid other parts of the welfare and social security budget to keep his savings on track.

At £92bn, pensions are the single most expensive part.

But he won't touch that pot.

Next, at £30bn are tax credits.

Which is the pot he already attempted to cut.

George Osborne needs a plan Tory rebel MPs can support. Credit: PA

So it's safe to assume he will find the money from the next biggest pot in the welfare budget: housing benefit, which costs £24bn per year.

If he does that, he can limit his tax credit cuts and still meet his self-imposed cap on total welfare spending.

What he must do, however, is present a plan which Tory rebel MPs can support.

And to do that, he needs to lessen the impact of the changes while better offsetting or delaying them.

What the House of Lords voted against (as did a number of Tory MPs in the Commons) was the plan to cut the income level at which tax credits started to be removed.

It's currently set at £6,420.

Mr Osborne wanted to start removing tax credits from those in work who earn £3,850.

The Government's tax credit reforms were defeated in the House of Lords. Credit: PA

His critics claimed that single change would cut £1,200 per year from those affected.

And yet, those losses would hit those in work and doing what the Government has been asking them to do.

So Mr Osborne's opponents will wait to see how he can cut less from tax credits and at the same time mitigate the reduction in earnings.

That could come in the form of higher national insurance thresholds, higher income tax personal allowance, more childcare help.

In short, there's no easy or straightforward way of cutting the £30bn bill for tax credits.