What if a transaction spans two different years?
Imagine you invoice a client on 1 March 2020, and they pay you on 1 May 2020. You've invoiced in one tax year, and been paid in the other one. Which year should it be in?
Meanwhile you're renting out a property and pay landlord insurance for 12 months starting on 1 January 2020. Do you need to apportion it?
The good news is that untied helps you follow the rules as simply as possible. For tax purposes, you can just look at when the cash comes in or out. Just find the relevant money in or money out and tag it.
(HMRC call this the "cash basis" and it is allowed as long as you're turning over under £150,000 for your business or property activity. The term for adjusting money between years is called the "accruals basis". So long as you're below the threshold, we like to keep it simple!)