Self Employed Income Support Scheme (SEISS) grants are taxed in the tax year in which they were received.

That means that grants one, two and three are taxable in 20/21 and should be reported in your 20/21 tax return. The fourth and fifth grants are taxable in 21/22.

You can include the value of the grants received for each tax year on the tax tab. Head to Self Employment, under income sources.