There is an exemption for this being taxed as a benefit in kind. In Section 317 Income Tax (Earnings and Pensions) Act 2003 there is an exemption if all employees of the employer concerned may obtain a free or subsidised meal. However, there is no requirement that all employees actually obtain the meals. The opportunity for all employees, at some time or other, to get a free or subsidised meal is enough to meet the terms of the exemption. However, if that opportunity is not open to all employees the exemption does
The exemption applies to meal vouchers only to the extent that those vouchers are tickets or tokens used to obtain meals on the employer's business premises or in a canteen open to the employees generally. It does not apply to meal vouchers used to purchase meals elsewhere. The meal vouchers should be non-transferable, only used for meals and the voucher issued should not exceed 15p for each working day.
If the exemption applies then all staff meals on a reasonable scale, provided on the employer's premises, are exempt from tax. This means that if all employees are entitled to a free or subsidised meal on the employer's premises or in a canteen, or meal vouchers, then working lunches on a reasonable scale, provided on the employer's premises, will also be exempt even if not all employees get the working lunches.
In short, if free meals are provided for the senior management team only then these are taxable, but free meals given in exchange for lunch time supervision for example, are not taxable, providing the opportunity to be included on the lunch time supervision list is open to all.