However, if person A is over the age of 18 and is in a position of trust to person B who is under the age of 18, it is illegal for A to engage in sexual activity with B. Section 47 of the Sexual Offences Act 2003 makes it an offence to pay for or promise payment for sexual services of a person under 18 where the 'client' does not reasonably believe that person is over 18, or in any event for a person under 13.