COBS 6.6.2 Definition

(a) A non-market price Transaction is a Transaction where the dealing rate or price paid by the Authorised Person or its Client differs from the prevailing market rate or price (after taking into account all costs) to a material extent or the Authorised Person or its Client gives materially more or less in value than it receives in return.
(b) Authorised Persons must undertake transactions at the prevailing market price. Failure to do this may result in an Authorised Person participating, whether deliberately or unknowingly, in the concealment of a profit or loss, or in the perpetration of a fraud.