Wpa Pool / Getty Images Each year, on the day after the UK budget, Britain's most influential think tank, the Institute of Fiscal Studies (IFS), delivers its verdict on the measures announced, and on the chancellor announcing them.On Thursday, IFS director Paul Johnson opened this year's briefing, and – at least by the standards of economic policy wonks – repeatedly burned the UK chancellor. 1. Dan Kitwood / Getty Images Let ye among us who has not found £27bn down the back of the sofa cast the first stone. That'd be almost all of us.Last November, George Osborne managed to deliver a series of popular giveaways thanks to optimistic economic forecasts from the Office for Budget Responsibility, who are responsible for predicting economic growth.Because they said the UK would grow quickly, they said Osborne wouldn't need to make so many cuts, as growth boosts tax revenue. This was used to slow the pace of cuts, boost personal allowances, and to introduce the living wage.But what the OBR give, they can take away. They're less optimistic now – much less optimistic – and so suddenly Osborne has lost £56bn. Oops. The rest of this year's budget was Osborne trying to make up this lost cash, ideally without us noticing too much. Unfortunately for him, the IFS noticed. 2. At times, the IFS director sounded a little....scary...in his assessment of the budget. Peter Macdiarmid / Getty Images What do you do when you've got to find £29bn to keep the promises you made when you got hired? That was the problem facing the chancellor in putting together the budget this year, and the IFS have been trying to work out how he solved it.He's hoping to find more cash by closing some corporate tax avoidance loopholes – which is fine, they say, so long as it works. He's made a few more cuts to departmental spending, though he's not going to explain what £3.5bn of those cuts are until 2018.But for the rest of it, he's relied on a little bit of sleight of hand. This IFS graph shows the £29bn disappearing behind the sofa (the down arrows) and where Osborne has found the cash to plug the gap. One of the labels is the pretty blunt "shuffling money".That bar is mainly thanks to a neat trick delaying when a change to how big companies pay tax is introduced. When the new system comes in, it will give a big boost to tax receipts for the first year or two after introduction, but this is just money being paid earlier than it used to: so in the years afterwards, there'll be less of it. It's a bit like getting an advance on your pocket money. Handily for the chancellor, though, that payback period is now pushed after the next election, and after his financial target."Very handy," said Johnson. 3. George Osborne has already broken his other rules, though. Peter Macdiarmid / Getty Images The IFS revealed that George Osborne now expects to break the rule he set himself on the welfare cap – a maximum cost to the government of working age benefits – not just once, but every year of the parliament.The chancellor also had to reveal during the budget that he now expects he'll breach a second, that borrowing as a percentage of the UK economy would fall every year of this parliament. Because growth is slower, the economy is smaller, and so he expect to break that rule by the end of this month.That explains why the chancellor is so keen to make his final target: a £10bn surplus by 2019-20, which helps explain why so much shuffling has been done to meet it.One effect of the reduced forecasts and the lack of "wriggle room", as Johnson put it, is to extend austerity another year. 2020-21 will now also see an extension of at least some of the lean times."Yet another year of austerity pencilled in," the IFS director said. 4. The IFS chief wasn't impressed by Osborne's claims on his tax changes, either Christopher Furlong / Getty Images George Osborne upped the personal allowance – the amount you can earn before you start paying income tax – to £11,500 in the budget. The trouble came when he claimed this meant 1.3 million people were "taken out of tax altogether".Low-paid workers still pay tax, and quite a lot of it relative to their incomes. Many low paid workers pay council tax, and VAT on anything they buy, and a whole bunch of other taxes.Most importantly, as Johnson noted in his speech, anyone earning more than "about £8,000" pays National Insurance, which is a tax levied on, er, your income. Or, as Johnson not-so-delicately put it: "Low paid workers are not taken out of tax by raising the personal allowance." 5. ...or his alcohol policy. Peter Macdiarmid / Getty Images Osborne froze duty on beer, cider and spirits during his budget (sorry, wine drinkers – he left you guys out).In his speech, the chancellor said the freeze on spirit duties was to help Scotch whisky exporters, who sell their booze around the world. There's a problem with this though: duty is paid on alcohol consumed in the UK, not alcohol produced in the UK. So whisky being exported is totally unaffected whether Osborne increases duty or not.Paul Johnson also suggested the decision to freeze duty on cider and spirits was somewhat strange given the government is committed to tackling problem drinkers."Spirits and strong cider are the tipples of choice among the heaviest drinkers," he said. "Their preference for strong cider at least is largely down to the fact that it bears much lower tax per unit alcohol than any other drink." 6. ...or the "sugar tax". Wpa Pool / Getty Images Part of the reason duty on alcohol works so weirdly (cider is taxed way less per unit of alcohol than anything else) is due to EU rules. These are particularly weird for wine, and lead to the amount of duty paid per unit of alcohol veering about wildly as wine gets stronger. Institute of Fiscal Studies As this graph shows, this has weird effects: The duty per unit of alcohol is lower for really strong wine (around 15% ABV) than it is for weaker ones, which probably isn't really what any policy maker intended. But rules are rules, and the UK is stuck with these ones (at least until the referendum in June).However, the new "soft drinks" tax, the IFS revealed, works in just the same way, with no EU around to blame at all. Institute of Fiscal Studies Next time you're buying a soft drink, analysis from leading economists show, if you want the most bang for your buck on the sugar tax, you should buy a ~really~ sugary drink – the maths speaks for itself.Or, of course, just buy a chocolate bar, which is totally exempt from the new levy. 7. And that's it! Well, except for calling poor George "confused and indecisive". Wpa Pool / Getty Images Over the last five years, George Osborne has often talked about his government fixing the mistakes of its predecessor. The IFS hinted he's now taken this a step further, by reversing a change he himself made to the UK tax system.The tax concerned is "capital gains tax" (CGT) – money made from the sale of assets (like shares), rather than from working. This is a tricky tax, as right-leaning governments tend to like to keep it low to encourage people to invest money, but making it low opens the door to clever tax dodges from high earners, who can find ways to turn their income into something that looks more like a "capital gain" (and save a fortune in tax in the meantime).To stop that kind of dodge, Osborne raised the top rate of CGT from 18% to 28% in 2010. Now, he's cut it from 28% to 20%, leaving us back where we started. Confusing? Just a bit. IFS Director Paul John's conclusion: "This is not the way to make good tax policy."Hope the chancellor has some ice for those fiscal burns.