It has long been held that tax is based on monetary values. Where no money changes hand, for example in a barter transaction, tax is due on the market value of the goods or services each party supplies. There can be VAT, PAYE, NI, and business tax on the transaction.
For example, if a sports club provides membership to someone in return for working a few hours a week in reception, this is a barter transaction. The club should declare the supply of a membership for VAT purposes. The worker should pay tax (and potentially national insurance) on earnings. Broadly, this would based on the normal value of the membership.
The March 2016 Budget has brought in rules to confirm that trading income received in non-monetary form is fully brought into account in calculating taxable profits for Income Tax and CT purposes. This will also apply to the calculation of taxable property income.