Income Tax (Earnings and Pensions) Act 2003 section 374

Non-resident or qualifying new resident employee's spouse's, civil partner's or child's travel costs and expenses where duties performed in UK

Section 374 provides a tax deduction for travel costs and expenses of the spouse, civil partner or child of a non-UK resident or qualifying new resident employee who performs duties in the UK, where those travel costs form part of the employee's taxable earnings.