Reality Check: Will the UK have to pay billions in tax refunds?
Claim: Vote Leave says membership of the EU means the UK will have to pay out up to £43bn in tax refunds to multinational businesses.
Reality Check verdict: The £43bn figure is not a definite commitment, it is what HMRC considers to be the most the UK might have to pay. It could be significantly lower depending on the outcome of current court cases. We don't know how much of it is connected to EU membership.
Vote Leave has highlighted a section of HMRC's Annual Report and Accounts which says £7.2bn has been set aside for legal claims (where taxpayers are disputing HMRC's assessments through litigation). It also refers to contingent liabilities (meaning possible liabilities from cases currently in litigation) of £35.6bn.
Adding the two amounts together gets Vote Leave to the £43bn figure.
We do not know if the full £43bn will be paid out or not. It is what HMRC currently considers to be the most the UK might have to pay if it lost every current case.
It is not clear how much of the contingent liability is connected to cases where the UK's membership of the EU has any impact.
Some of it might be - cases can end up in the European Court of Justice if EU law is involved - but HMRC cannot disclose details of what the cases are or how much is potentially at stake in each case.
UPDATE: This article was modified on 7 June to emphasise the uncertainty over how much of the money in question will be paid out.