If her ex husband has already paid tax in full on the money she is receiving then she should not have to pay tax on it' that would be double taxationu00a0u00a0u00a0 BUT if he treats the money he gives her as a deduction from his gross earnings then she is receiving untaxed income and she will have to pay tax on it. If any tax is to be paid it will be payable in the country she is now in permanent residence. So if she spends part of the year inthe US and part in GB then theu00a0 she must decide which is her pemanent residence and this will normally be the one she spends most time in and/ or the one she has a permanent home