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HMRC internal manual

Employment Income Manual

Employment income: scale rate expenses payments: accommodation and subsistence payments to employees travelling outside the UK: employee staying as guest of a private individual

In cases where an employee stays as a guest of a private individual (including a colleague), and has to pay for neither their accommodation nor meals, employers may reimburse, per day, 10% of the appropriate total residual rate to cover a gift for the host, for example. Any meals that the employee does have to pay for may be reimbursed using the appropriate meal rates.

See example 4.