Non-decimal currency Non-decimal currency A non-decimal currency is a currency that has sub-units that are a non-decimal fraction of the main unit, i.e. the number of sub-units in a main unit is not a power of 10. Today only two countries in the world use non-decimal currencies. Both of these countries are in Africa. These are Mauritania (1 ouguiya = 5 khoums) and Madagascar (1 ariary = 5 iraimbilanja). However these are only theoretically non-decimal, as in both cases the value of the main unit is so low that the sub-unit is too small to be of any practical use and coins
Legal tender of this are: Individual coins or banknotes can be demonetised and cease to be legal tender (for example, the pre-decimal United Kingdom farthing or the Bank of England 1 pound note), but the Bank of England does redeem all Bank of England banknotes by exchanging them for legal tender currency at its counters in London (or by post) regardless of how old they are. Banknotes issued by retail banks in the UK (Scotland and Northern Ireland) are not legal tender, but one of the criteria for legal protection under the Forgery and Counterfeiting Act is that banknotes must be payable