tax year

Income flows continuously, but tax cannot be calculated on a never-ending stream — at some point you have to draw a line, add up what happened, and settle the bill. The tax year is the fixed twelve-month period a government uses to measure income and figure the tax owed on it. It is the calendar against which all your earning, spending, and tax events are sorted.

For most individuals, the tax year is the calendar year, running January 1 to December 31, so income earned in that span and the deductions claimed against it all belong to that single year's return. But it is not always the calendar year: some countries set a different annual cycle (the United Kingdom's personal tax year, for instance, runs to early April), and many businesses are allowed to choose a fiscal year that ends when their activity is quiet rather than on December 31 — a ski resort might end its year in summer. Whatever the dates, income and expenses are assigned to the year in which they fall, and the tax is computed on that year's total. A purchase on December 31 lands in one tax year; the same purchase on January 1 lands in the next.

The tax year matters because it sets the cut-off that decides which year an item is taxed in, and that timing can change how much tax is paid and when. It also drives deadlines: filing and payment dates are tied to the end of the tax year. A company's fiscal year for financial reporting and its tax year are often the same, but they need not be, and accountants must keep clear which calendar a given figure follows.