Executive Rule No. 37 outlines the tax treatment of foreign exchange rates and currency conversion gains and losses. It stipulates that foreign exchange rates against the Kuwaiti Dinar must align with Central Bank instructions, using the annual average rate. The Rule distinguishes between realised and unrealised (book) profits and losses. Realised profits from transactions are allowed, and realised losses are accepted with supporting documentation. Conversely, book profits and losses arising from the revaluation of assets and liabilities are not recognised for tax purposes.