If you are a salaried employee and you have expenses your employer has not reimbursed you for (e.g business mileage, uniforms, professional subscriptions etc) you can claim tax relief on these.

For example, if you are a higher rate taxpayer and had £1,000 of job expenses, you can claim back £400 from HMRC.

DO NOT use a tax refund firm. Their fees are extortionate. Do it yourself via HMRC’s portal. You can claim back for up to 4 tax years, and it’s quick and simple.

https://www.gov.uk/claim-tax-refund/y