A collective investment vehicle has a single price if investors can buy and sell stakes in it at exactly the same price.OEICs and investment trusts single priced. Unit trusts and ETFs are dual priced: the buying and selling prices are different.
Single priced vehicles are not necessarily cheaper to buy and sell than those that are dual priced. It is common for OEICs and unit trusts to make an initial charge when you buy (or sometimes an exit charge instead). This often more than makes up for the lack of a spread.