I need to do my self assessment. Can I do it on this site?

Thanks for dropping by the Community, @sjs75.

The option to submit your Self Assessment tax return through QuickBooks Online (QBO) is currently not possible. This feature is only exclusive to QuickBooks Self-Employed (QBSE).

What you can do is use the income and expenses information on the Income Tax page in QBO to help generate an estimate of your Income Tax. You can read this reference for more details: Understanding Income Tax.

If you’re filing a Self Assessment tax return for the first time, you’ll need to register with HMRC first. Once registered, you’ll get a confirmation email with your 10-digit Unique Taxpayer Reference (UTR), user ID, and password. After you receive your UTR, you’ll need to sign in to your personal tax account to activate your Self Assessment.

Moreover, check out this article for a complete guide to submitting a Self Assessment tax return and the checklist to help you get started: Self Assessment for Income Tax checklist for QuickBooks Online.

Please keep in touch if you have further questions about filing a self-assessment tax return. I'm always here to help. Have a great day!