If you've ever wondered why the UK tax year begins on April 6th instead of January 1st like most countries, you're not alone. It’s a peculiar quirk of British history—one rooted in medieval traditions, lost calendar days, and a government that wasn’t willing to lose out on tax revenue.
Centuries ago, the UK tax year actually began on March 25, a date known as Lady Day. This was one of four Quarter Days in medieval England—important dates when landlords collected rent, debts were settled, and contracts were renewed.Lady Day also had religious significance, marking the Feast of the Annunciation, when the angel Gabriel supposedly told Mary she would give birth to Jesus. For generations, it made sense for financial matters to align with agricultural cycles and religious observances.But then, in the 18th century, everything changed.
By the 1700s, Britain was still using the Julian calendar, which had been around since the days of Julius Caesar. The problem? It was 11 days behind the rest of Europe, which had switched to the more accurate Gregorian calendar introduced by Pope Gregory XIII in 1582.So in 1752, Britain decided to catch up. But instead of gradually fixing the issue, the government simply deleted 11 days from the calendar, meaning that September 2, 1752, was immediately followed by September 14, 1752.The British public was outraged. Some people thought their lives had been shortened, while others protested in the streets, demanding their stolen days back.But the biggest headache? The government realised that if the financial year still ended on March 25, they would lose 11 days of tax revenue. And that was unacceptable.
To make sure the Treasury didn’t lose money, the government extended the tax year by 11 days, pushing it from March 25 to April 5.Then, in 1800, another minor adjustment was made, pushing it one more day to April 6—where it has remained ever since.
Even though this date originated from an 18th-century calendar problem, it still governs major UK financial rules, affecting:✔ Income tax calculations ✔ ISA allowances ✔ Pension contributions ✔ Corporation tax deadlines
While most countries align their tax years with the calendar year, Britain continues to follow this historical oddity, proving that tradition (and tax collection) always comes first.
💡 Next time you file your tax return, remember—Britain’s tax system was designed to fix a calendar mistake from 1752. If that’s not peak British history, what is?