At first glance, it seems like exactly the sort of thing Britain should have sorted out by now. Most countries manage perfectly well with a calendar year. We, on the other hand, prefer to begin our tax year just as spring gets going, which is not especially intuitive but is, in its own way, very British. The short answer is that it is historical.
For individuals, the UK tax year runs from 6 April to 5 April. That timing affects income tax, capital gains tax and many annual tax allowances and tax planning deadlines. It is also worth saying that this is not the same as the government’s financial year, or the accounting year many companies use, which typically runs from 1 April to 31 March. That distinction is one reason the whole subject can feel more confusing than it ought to.
The story begins with what used to be known as Lady Day, one of England’s traditional quarter days. Lady Day fell on 25 March and, for many years, was treated as the start of the financial year. Quarter days mattered for rents, contracts and accounts, so this date carried real practical weight.
The complication came in 1752, when Britain adopted the Gregorian calendar. Much of Europe had moved earlier, but Britain had stayed on the Julian system for longer. To bring the calendar back into line, 11 days were omitted in September 1752. That meant the old Lady Day date of 25 March shifted to 5 April in the new calendar. The tax year, already tied to that old quarter day tradition, moved with it rather than being reset to 1 January.
So why 6 April rather than 5 April?
The usual explanation is that a further adjustment followed around 1800, when leap year treatment differed between the Julian and Gregorian calendars. The broad result is the one we still live with today: the UK tax year starts on 6 April and ends on 5 April.
In other words, the UK tax year does not begin on 6 April because it is logical. It begins on 6 April because history got there first, and the modern tax system grew around it.
Now that another tax year-end has come and gone, it is a useful reminder that while the date itself is a historical quirk, the planning around it is best approached with a little less last-minute drama.
