Before we get on to any of the numbers – from Rishi Sunak’s claim about Labour raising taxes by £2,000 to the more outlandish numbers going around today – here’s the most important thing you have to know right now.

The parties fighting this election have yet to publish their manifestos. They might come as soon as next week, but until those documents, with their shopping lists of confirmed policies, actually land, we are in a kind of policy no man’s land where each side is guessing (and sometimes plain making up stuff) about what the other side actually wants to implement if they win the election.

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And since all parties like to talk a lot about exciting new things they’d spend money on and not half as much about the taxes they’d raise to pay for all that stuff, it doesn’t take a mathematical whizz to realise that if you take them all quite literally then you can impute some pretty big “black holes” in their plans.

Those “black holes” matter because both Labour and Conservatives have signed up to fiscal rules preventing them from splurging without limit. So if there is a hole, the assumption is it would have to be filled by raising taxes.

However, in the absence of either manifestos or detailed costing plans, the best we can do about all this for the time being is to speculate.

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Does Sunak’s claim about Labour taxes stand up?

That brings us back to the claim Rishi Sunak made in last night’s debate, that Labour will raise everyone’s taxes by £2,000. This is a direct consequence of this information vacuum.

It comes from a “dossier” published by the Tories last month, back before the election was called, which purported to calculate all Labour’s proposed tax and spending plans.

The headline finding from that paper was that over the course of the next four years Labour had roughly £59bn of spending plans (at least as far as the Tories claimed) but only £20bn of revenue raising plans. That leaves a £39bn hole. Divide that £39bn by the number of households in the country (18.4m) and you get a figure of just over £2,000. Voila: £2,000 of unaccounted tax rises or spending cuts which, said Rishi Sunak last night, would inevitably be filled with extra taxes.

Now, there are all sorts of objections to the way the Conservatives have carried out this exercise. For one thing, they deployed a weapon Labour don’t have: because they’re the party of government they were able to ask Treasury civil servants to cost some of the Labour policies (or rather, the policies they think Labour will implement – remember, those manifestos haven’t yet been published!).

Today there has been a backlash – including from the Treasury’s permanent secretary himself – about the way the Tories have portrayed these sums.

What the Tories have already cost households

The £2,000 figure isn’t really a Treasury calculation or for that matter an “independent” one, as Mr Sunak called it last night. It’s a Conservative figure – but it was put together in part with figures commissioned from civil servants.

There were other objections: Labour say many of the policies in that Tory dossier won’t cost half as much as the Conservatives claim.

But actually, surprising as it might sound, what’s most striking about this “bombshell” is how small it really is. Less of a bombshell; more of a hand grenade.

While £2,000 sounds like a big number, it’s actually a cumulative total from four years. A far more representative figure to take from the dossier is £500 – the annual figure.

And while that’s not to be sniffed at (if you believe it – which you probably shouldn’t) it’s far, far smaller than the tax rises we’ve all experienced under this Conservative government since 2019. They amount, all told, to an average of around £3,000 a year per household or, if we grit our teeth and tot it up as the Tories did in their dossier, over £13,000 over the course of the parliament. Which rather dwarfs that £2,000 figure.

Labour attack dossier is even more outlandish

So anyway, you’re probably hoping now we’ve explained the £2,000 from last night that we could leave things there. But sorry, no.

Because, this being the murky pre-manifesto period, Labour have gone one further and produced their own dossier, purporting to show Conservative fiscal plans for the coming years. But while the initial Tory document was somewhat conservative (with a small c) about its numbers, the Labour version is far more outlandish.

It assumes, for instance, that the Conservatives are planning to abolish National Insurance and inheritance tax overnight if they are elected. These are mammoth tax changes which the Conservatives have never committed to (they have made some vague noises about intending to abolish NICs but not in the next parliament).

Anyway, the Labour document takes these and other policies and works out that that would imply a black hole of roughly £70bn a year or a whopping £270bn when you tot up the first four years of the parliament (they actually provide five years of numbers but for the sake of comparability I’m looking solely at the first four years, as the Tories’ dossier did).

Divide that by the number of households (as the Tory document did) and you end up with a grand total over those four years not of £2,000 but of a staggering £14,000 per household.

Parties trading blows in the realms of fiscal fantasy

At this stage, now we’ve completely departed from realistic policy, you’re probably wondering when this silly saga will be over. Sadly the answer is: not yet.

Because having seen the Labour response, the Conservatives produced a second dossier, essentially saying: “Well, if you’re going to make all sorts of outlandish assumptions about the stuff we’ve vaguely talked about then can we have a go too?”

This final dossier includes all sorts of policies no one seriously expects Labour to implement this parliament: cutting corporation tax to 12.5%, scrapping business rates altogether, introducing French-style union laws. Add this all up and you end up with a grand total of £211bn a year or – if you multiply that by four years across a parliament, £844bn. So the best part of a trillion pounds.

We are of course in the realms of fiscal fantasy at this stage, but if you take that cumulative total and divide that by the number of households in the country you end up with an utterly ridiculous figure of £46,000.

Whether either party thinks these dossiers will change anyone’s mind in this election remains to be seen.

Right now they mostly look like an attempt to send economics correspondents completely crazy.

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Both major parties are committed to tax rises

But the overarching point is as follows: both the major parties are committed to tax rises in the coming years. We know as much because the official Office for Budget Responsibility plans will see the tax burden increase sizeably, in large part because the main tax-free allowances are being frozen, ensuring everyone ends up paying more tax, once you adjust for inflation and rising wages.

These tax rises – the long-term consequences of the pandemic and the energy price guarantee – are quite likely to dwarf any measures we hear about in the coming manifestos.

But until we get those manifestos, the rest is, yes, speculation.