Anyone whose income is not fully taxed at source or whose circumstances require HMRC to look at the whole picture. That means the self-employed, partners, most landlords, company directors with untaxed income, people with significant savings, dividend or foreign income, anyone with capital gains to report, and higher earners caught by the child benefit charge or the tapering of the personal allowance. Being a director does not by itself require a return, contrary to a widespread belief — if all your income is taxed under PAYE and you have nothing else to declare, you may not need to file. Conversely, having a modest side income can bring you in. If HMRC has issued a notice to file, you must file, even if you owe nothing, until they withdraw it.