Hi, I think there’s some sort of error on my self-employed app where it’s calculating this tax year from Jan 1st 2021 instead of April 4th 2020....how can I solve this? Is this to do with Brexit...?

Hi @rebeccaleggett-b,

For QuickBooks Self-Employed (QBSE), it will start to calculate your taxes at the start of your self-employment date. 

If you have transactions before your self-employment date, then these will be ignored in your Self-Assessment Summary. To check your self-employment date, follow the steps below:

1. Go to the Gear icon. 
2. Select Tax Profile. 

Check out the screenshot below for your reference:

As for the changes brought by Brexit, you can view this article: Brexit FAQ. It's a list of common questions our users have for QuickBooks Online and QBSE about this process, along with their answers. 

Post a reply if you have other concerns about your tax profile in QBSE. I'll be around to help you out.