The basis period is the period of time used to calculate an individual's or business's taxable income for a given tax year. The basis period is typically the same as the tax year, but there are some circumstances in which it may be different.

For individuals, the basis period is typically the tax year in which the income was earned. For example, for the tax year 2021/2022, the basis period would be the period from April 6, 2021 to April 5, 2022.

For businesses, the basis period may be different depending on the type of business and the nature of the income. For example, a business with accounting periods that do not align with the tax year may have a basis period that spans multiple tax years.

It is important for individuals and businesses to understand their basis period, as it determines when they are required to report their income and pay taxes.