Tax year
What it really means
The UK tax year runs from 6 April to 5 April the next year, not January to December. Allowances, tax bands and many rates reset on 6 April, so figures are often quoted per tax year.
Context, tips & common mistakes
The 6 April start date trips people up in practical ways. Job adverts, salaries and allowances all reset against that date, so 'this year's' figures in January belong to the tax year that started the previous April. After each year ends, HMRC reconciles PAYE automatically — a calculation letter saying you overpaid is normal and the refund route is free, while a letter saying you underpaid usually just adjusts a future tax code rather than demanding a lump sum.
The tax year also drives every deadline that matters to the self-employed: registering for Self Assessment, filing, and paying all key off the 5 April year end, and missing them brings automatic penalties even when no tax is owed. When comparing anything financial — pension contributions, student loan repayments, savings allowances — always check which tax year a figure belongs to before relying on it.