A Postal Order is used for sending money through the postal system. Postal Orders can be bought and redeemed at post offices in the UK, and come in fixed denominations. Post Orders are not, strictly speaking, legal tender, in the way that banknotes are, but are a type of promissory note, similar to a cheque. The fee for using this form of payment tends to be around 8%. It was a safe method in times past, but nowadays offers very little advantage over cheques or electronic transfer .