AFTER their failed attempts to overhaul Barack Obama’s Affordable Care Act, Republicans in Congress are eager to move onto a subject where there is more agreement: tax reform. Republicans all think that taxes should be lower. Even many Democrats want the corporate tax rate to fall (it is currently 35%, the highest rate among rich countries). And Republicans can use the “reconciliation” procedure to get tax cuts through the Senate with just 51 votes. They are planning to take up tax reform when they return from their August recess. Vice-president Mike Pence has promised “the largest tax cut since the days of Ronald Reagan”. But this will be tricky to achieve. Why?

There are both political and procedural barriers to tax cuts. Take the corporate tax. Politicians tend to claim that they could afford to cut the rate if only they closed loopholes. Yet every deduction has its defenders. The biggest and baddest carve-out in the corporate tax code exempts companies’ debt interest payments from the calculation of profits, but the Trump administration seems to have little appetite to scrap it. The largest tax breaks for specific industries go to domestic manufacturers and oil and gas producers—sectors close to Mr Trump’s heart. America’s rate is so high in part because it has unusually generous deductions for investment. But economists who favour tax cuts tend to think that such deductions boost growth more than rate cuts do. In fact, many Republicans want to expand them.

Congress could pass unfunded tax cuts that raise the deficit. But there are procedural hurdles to doing so. Before they can use reconciliation, Republicans must pass a budget. That means deciding whether—and to what extent—tax cuts will be paid for. Early drafts of the budget in the House of Representatives would not increase deficits, but congressmen are already fighting over how to make the books balance. As a result, the budget is behind schedule. To allow unfunded tax cuts, the budget would have to waive Senate rules preventing bills from adding to deficits (even then, tax cuts could probably only last ten years). Republicans would also need to circumvent a law, signed by Barack Obama in 2010, that triggers automatic spending cuts if lawmakers pass costly bills. These cuts would fall on programmes including Medicare, health insurance for the old, which Mr Trump has pledged to protect.

These barriers are not insurmountable. Various parliamentary tricks, such as lengthening the ten-year budget window, changing the budget “baseline”, or instructing bean counters to assume much faster economic growth, could all help. But fiscal hawks may well object to undermining the budget process. If, as seems more likely, tax cuts have to be genuinely revenue-neutral, Mr Trump, who often speaks of slashing business taxes to 15%, will need to drastically curtail his ambition. Most Republicans seem to agree that individuals should not be able to deduct state and local taxes from their federal tax bills (those from high-tax states like New York and California are a notable exception). Scrapping that rule would raise money for modest permanent tax-cuts for individuals. They could be paired with a temporary corporate tax cut, funded by taxing profits that firms have, until now, stashed overseas. Such a package would be more than nothing. But it would be much less than Mr Trump and others have been promising.