Actually, it's all a bit vague at this stage. We don't yet know whether the cuts will even be announced before Christmas, let alone when they'll be delivered. Nor do we have any idea whether they'll be large, small or indifferent.

Wouldn't surprise me if they were on the small side, nor if we got them only as a reward for voting Turnbull back into office at the next election, to be held late next year or in the middle of 2019.

All we actually know is what Turnbull dropped into a speech to the Business Council after affirming his intention to press on with the hugely expensive company tax cuts for big business.

"In the personal income tax space, I am actively working with the Treasurer and my cabinet colleagues to ease the burden on middle-income Australians, while also meeting our commitment to return the budget to surplus," he said.

It wouldn't surprise me if even Turnbull doesn't yet have a clear idea about the size and timing of the cuts. That will depend partly on Treasury's grudging willingness to make it seem they can be afforded "while also meeting our commitment to return the budget to surplus", but just as much on the calculations of his spin doctors.

Will they decide to announce the cuts soon, using them as attempt to break the circuit of negative media discussion of some problem the government's having, or keep them under wraps until much closer to the time when voters are asked to show their gratitude at the polls?

That Turnbull has dropped the big hint this early in the piece is a sign they're more likely to be chewed up in a desperate but futile attempt to give the government some "clear air", than carefully preserved as part of a grand re-election strategy.

But though uncertainty abounds, there are three iron laws of tax cuts.

The first is that a government's motive in making them is always mainly political. It either fears that if it doesn't cut it will lose votes - because voters are starting to resent how much tax they're paying on any pay rises or overtime - or it hopes if it does cut this will win votes in thanks for its magnanimity.

The second law is that, despite their political motivation, tax cuts always come colourfully wrapped in wonderful economic justifications. By taking this political gift, we're assured, we'll be creating jobs, reducing unemployment and making the economy grow.

It's almost our economic duty to accept the offer of the bloke selling tax cuts for votes.

The third law, however, is that voters' gratitude for being given a little of their own money back is faint to non-existent. A tax cut announced is soon forgotten; a tax cut delivered before an election has next to no influence on the outcome.

But can the budget afford tax cuts? Not if you accept the government's preferred way of measuring the deficit. It says we're still a long way from returning the budget to balance.

The government's prediction we'll be back to budget surplus by 2021 rests heavily on its forecast that wages will soon start growing strongly, much faster than inflation. Maybe.

If Treasury finds a way to maintain that trajectory while paying for tax cuts, it will be by stepping up its over-optimistic forecasts of wage growth. With circular logic, the "bracket creep" such forecasts imply would then be used to justify the tax cuts themselves.

For years we've been told a government that needs to borrow each month to keep itself afloat can't possibly afford to give aid to poor people overseas. But borrowing to cover tax cuts to big business isn't a problem nor, apparently, is borrowing to give voters a tax cut.

The sad truth is that this Abbott-Turnbull government has got neither the conviction nor the honesty to stick to a consistent line on debt and deficits.

In opposition they told us the debt was a frightening crisis, but easily fixed by them. In government they had one go at fixing it at the expense of everyone but their own supporters, but lost public support from that moment, and since then have abandoned any serious attempt at budget repair, merely waiting like Mr Micawber for something (bracket creep) to turn up.

Now it's decided it can't wait even for that, but must give some of it back on the assumption it will turn up - eventually.

But whatever their political motivation, tax cuts do have effects on the economy, so what would they be?

At a time like this, tax cuts would have a similar effect to a decent pay rise, making it a little easier for households to keep spending, giving consumer spending a modest boost and, indeed, creating a few more jobs.

And if you defy federal Treasury and measure the budget balance more sensibly, stripping out investment in infrastructure, you find the recurrent deficit has already been largely eliminated. A small tax cut wouldn't set it too far off course.

Ross Gittins is the Herald's economics editor.