Why does the UK Tax Year start on 6th April?

Option A:

What seems like a simple question actually has a complex history!

Up until 1752, England used the Julian Calendar, introduced by Julius Caesar in 46 BC. Two different systems were in use: the calendar year officially started on January 1st, but for legal and tax purposes, the year began on March 25th, known as “Lady Day,” the day the Virgin Mary’s announcement is celebrated. Meanwhile, most of the rest of Europe had already switched to the Gregorian Calendar in 1582, thanks to Pope Gregory XIII. He made the change because the Julian Calendar had drifted out of sync with the seasons.

It took two more centuries before Britain finally adopted the Gregorian Calendar in 1752. Before that, dates between Britain and the rest of Europe were out of sync—not only by 11 days, but also because the calendar years were calculated differently. In England, the period from January 1st to March 24th counted as the end of one year, while the rest of Europe considered January 1st as the start of the year.

In 1751, the British government passed the Calendar Act, aligning England with the rest of Europe. For the first time, the year started on January 1st and ended on December 31st. But that wasn’t all. Later in 1752, the calendar was adjusted by skipping 11 days—going from September 2nd directly to September 14th—so the dates would match those on the continent.

This caused a bit of an uproar with tax collectors. They still counted a full tax year from Lady Day (March 25th) in 1751 to Lady Day in 1752, and again the following year. But because 11 days had been “lost” when the calendar changed, the 1753 tax year ended not on March 24th, but on April 5th. And since then, the UK’s tax year has ended on April 5th.

You might think that to make up for the 11 lost days, the tax year should have ended on April 4th. However, 1752 was a Leap Year. Even though the period from January 1st to March 24th was effectively “wiped out” of existence, that time still included February 29th, and the tax authorities counted all 366 days.

This is a simplified explanation. The situation was more complicated in Scotland, which had already started the New Year on January 1st as early as 1600. In England, the New Year used to start on December 25th until the 14th century. And it’s also worth noting that the Gregorian Calendar, to account for the fact that a solar year isn’t exactly 365.25 days, only includes Leap Years in centennial years every 400 years. So, the years 1800 and 1900 weren’t Leap Years, but 2000 was.

And that’s all there is to it!

Option B:

Because it does, do not worry about it!