To prove a referee's professional standing, the Home Office accepts several categories of documentation. For active professionals, an employer's letter on official letterhead, employment contracts, payslips, P60s, or tax records serve as primary evidence [1]. Self-employed individuals should provide tax returns, business registration documents, or invoices [1]. For retired referees, pension statements, retirement letters from former employers, or historical professional membership certificates establish prior standing [1].

Where a profession is regulated—such as medicine, law, or engineering—providing a registration number allows direct verification against official registers maintained by bodies like the General Medical Council or Law Society [1]. All documentation should ideally be dated, signed, and include the person's full name, job title, organisation, and employment dates [1]. Identity verification via passport is required in all cases. If no formal register exists, a direct letter from the employer, HR department, or professional body provides the clearest proof [1].