Hello, Oliver. Submitting tax returns to HMRC through the app is currently unavailable.
The QuickBooks app is designed only for managing transactions, customers, creating invoices/estimates, and running Profit & Loss reports. Filing tax returns can be done either in your mobile browser or a web browser.
Here's how:
Sign in to your QB Sole Trader on any web browser.
Head to Taxes.
Then click on Join MTD for Income Tax pilot on the top right of your screen.