Deep Dive + Myth-Busting for the curious Business Owners & Accountants
If you’ve ever paused and thought, “Why does our tax year start on 6 April – not 1 January like most places?” you’re not alone.
That odd date carries centuries of history, legal technicalities, and also misinterpretations.
The simple answer is that the Government didn’t want to lose 11 days worth of taxes.
Let’s trace the historical journey from Lady Day through calendar reforms, Unpack the legal and drafting intricacies that fixed the date, Investigate and debunk alternative theories (including those invoking India, harvest cycles, East India Company)
Let’s begin.
Going Medieval: The Starting Point of the financial year Starting in April: Lady Day (25 March) and Medieval Financial Practice
Quarter Days, Rents, Contracts & New Year
In medieval England and Wales, the calendar of obligations, rents, leases and accounts often revolved around quarter days, fixed dates each year when sums were due, leases renewed, contracts settled.
The quarter days included: 25 March (Lady Day), 24 June (Midsummer), 29 September (Michaelmas), and 25 December (Christmas).
Lady Day (25 March) was significant in multiple ways. Many financial and land-tenure arrangements used 25 March as their “year start” for rents, leases, etc. It was tied to the Christian calendar (the Feast of the Annunciation) and was considered one of the key “new year” or legal year points in older English custom.
When historians study old tax statutes or land tax acts, they often refer to assessments “from” 25 March.
So, for centuries, many administrative and fiscal cycles aligned with that 25 March “anchor.”
The Great Calendar Shift: From Julian to Gregorian
Why Change? The Drift of the Julian Calendar
The Julian calendar (introduced by Julius Caesar) was widely used for many centuries, but it drifted slightly relative to the solar / astronomical year to the tune of about 11½ minutes per year.
Over centuries, that added up: by the 1500s, the calendar had drifted 10 days out of sync with solar / seasonal time.
Pope Gregory XIII introduced the Gregorian calendar in 1582 to fix this drift (skipping certain leap years, removing days, realigning).
Many European nations adopted it quickly; Britain (being Protestant and politically wary of a Papal reform) delayed.
Britain Finally Conforms (1752)
In 1752, Britain passed legislation (the Calendar (New Style) Act 1750) to switch to the Gregorian calendar. Part of this involved omitting 11 days in September: after 2 September came 14 September. That made up for the accumulated drift.
However, that gave rise to a thorny question: if you simply “delete” 11 days, many tax, rent, and accounting cycles (which expected full years) would be disrupted. The Treasury and Parliament needed a workaround.
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The Fiscal Workaround: Preserving a “Full Year” & Shifting the Tax Year
“No Tax Revenue Lost” — The Treasury’s Reaction
To avoid “losing” tax revenue because of the missing 11 days, the government decided not to shorten the tax/financial year. Instead, they extended or shifted the relevant tax cycle so that the same amount of time would still be captured, effectively pushing the start of the cycle forward.
Because the original tax year (in the “old style” Julian-based system) had been anchored to 25 March, the shift resulted in a new “start” date of 5 April under the new calendar. (Why 5 April? Because 25 March “plus 11 omitted days” corresponds to around 5 April.)
In short: tax assessments that used to run from 25 March (old system) were reinterpreted, under the calendar shift, to begin 5 April (new style).
Leap Year Adjustments and the Move to 6 April
The story doesn’t end on 5 April. Because of the way the Gregorian calendar handles leap years (skipping some century leap years unless divisible by 400), an additional adjustment was made in 1800 (a year that would have been a leap year under Julian rules but was not under Gregorian). The Treasury pushed the cycle by one more day so that the “tax year start” moved from 5 April to 6 April.
Some detailed sources note that in 1900 the Treasury abandoned one tricky tweak, but by that time 6 April was sufficiently entrenched.
One key technical point: old statutes used the word “from” (as in “tax year from 25 March”), which by a legal interpretation rule of the time meant “starting the day after” — i.e. using “from 25 March” might legally start 26 March. That interpretive rule further nudged how dates shift when transplanting old-style dates to new ones.
So, the origin of 6 April is a combination of calendar correction, legal interpretation, and desire to preserve full years of revenue.
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Myth-Busting & Alternative Theories
Over time, a number of alternative theories have circulated to explain the 6 April tax year — some plausible, many fanciful. We’ll examine the stronger ones and separate more myth from likely fact.
Myth: It’s Because of India or the Harvest Season
One of the more colourful claims you’ll see via informal circles is that the UK tax year start reflects an Indian agricultural cycle (e.g. after a harvest) or that the East India Company imposed this date to align with Indian practices.
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Harvest cycle theory: The idea is that, during British colonial involvement, the East India Company or colonial tax systems aligned revenue collection with post-harvest periods (when farmers had cash), and that tradition carried back to the UK. This is not supported by good historical evidence. There is scant credible scholarship linking Indian seasonal tax cycles to the British personal tax year date.
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East India Company influence: Some suggest the Company “imported” a tax calendar based on its Indian operations into British legal practice. In reality, the East India Company was primarily a commercial and political entity in India, not an institution that dictated domestic British tax law.
The shift of calendar systems and tax cycles in Britain predates substantial British ruling authority in India and long predates the full administrative formalisation of the British Raj. The transition from Julian to Gregorian and associated British internal adjustments had nothing to do with Indian farming cycles.
Thus, while exotic and appealing, the “India/harvest” theory is overwhelmingly considered a myth or later speculation by credible historians.
Myth: It Was Arbitrarily Chosen or Just Tradition
Another weaker—but less exotic—theory is that the Treasury or government arbitrarily picked 6 April and it just “stuck.” That’s also misleading: the date is not arbitrary; it results from systematic adjustments for days lost and leap-year idiosyncrasies.
Theory: It’s so Accountants get a Christmas break
It’s not accurate that the tax year exists in it’s format in the UK to give accountants and bookkeepers a break. It’s likely a myth come into being from a joke, probably originally from an accountant. Of course accountants are famous for their humour.
Theory: Changing It Would Be Too Painful — So It’s Just Inertia
This is less a myth and more a realistic explanation for why it persists: the costs of re-engineering tax systems, software, payroll, legal definitions, public familiarity, administrative systems are enormous. So even though “rational” alternatives (e.g. aligning tax year with calendar year) get proposed from time to time, inertia and cost act as barriers.
Indeed, in 2021 the Office of Tax Simplification reviewed options for moving the tax year end to 31 March or 31 December, but concluded that the burdens of change were significant enough to resist overhaul.
The Modern Tax Year & Why It Still Matters for You (Business Owners / Accountants)
The Structure Today
Today, the personal tax year in the UK runs from 6 April to 5 April of the next year. That is when individuals compute income, deduct allowances, and settle liabilities.
That is distinct from the UK government financial year, which runs 1 April to 31 March (used for budgeting, public accounts), and also distinct from many companies’ accounting years (which might align with calendar year or any convenient 12-month period).
Because of this, business owners often juggle multiple overlapping “years” — e.g. their company accounts, corporate tax returns, and personal tax assessments.
Why This Odd Date Still Matters
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Tax Deadlines and Planning
If you don’t internalise the 6 April start, you may miscalculate deadlines, miss opportunities for tax planning (e.g. pre-year contributions, harvesting losses), or misalign your business cash flows. -
Year-end Alignments / Accounting Efficiency
Many companies choose a year end (say 31 March, 30 June, 31 December) for operational reasons; understanding how those align (or don’t align) with the personal tax year helps with integrated planning. -
Communication Clarity
If you can explain quirky things like “why 6 April” to your clients or staff, you convey competence, credibility, and domain mastery. -
Change Proposals & Structural Risk
If governments someday again consider changing the tax year, knowing the history helps you assess proposals, adapt early, or advocate for alignment.
If you’re reading this because you’ve found yourself scratching your head over dates, deadlines, or how your business numbers “fit together,” or even because you’re putting off tackling your taxes – here’s what I suggest:
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