The US Treasury Department has issued proposed guidance for determining a foreign partner's taxable gains or losses from a transfer of its interest in a partnership engaged in a US trade or business. The new regulations give effect to measures in the Tax Cuts and Jobs Act 2017 designed to overrule the US Tax Court's unexpected decision in the Grecian Magnesite Mining v Commissioner case, which prevented the Internal Revenue Service from taxing a foreign partner's gains from disposal of its partnership interest.