I can I start a new year of accounts and file last years?

Hi there. @Tracey11_2 2. To start a new tax year, make sure you've already setup the First month of the tax year in Settings > Advanced > Accounting. 

See screenshot below:
 

 
To file last year’s tax return, make sure you’re registered with HMRC and your setup is correct. Complete the checklist in QuickBooks, then enter your information into HMRC’s Self Assessment portal.

Follow these steps:

1. At the bottom of your tax summary, select Export.
2. Open the exported file and copy the totals.
3. Sign in to HMRC’s online service.
4. Paste the figures into the correct boxes and submit your return.
5. HMRC will confirm your submission with a reference number.

For more information about filing tax returns, refer to this resource: Self Assessment for Income Tax: Checklist for QuickBooks.
 

Let us know if you have further questions or concerns.