Welcome to the Community, @mrichards2271.

The taxReturnInvalidMTDEndDate error occurs because either you’ve attempted to file too early or your Making Tax Digital (MTD) permissions aren’t fully set up.
 

To resolve this issue, wait until the end of the tax period before submitting your return. Next, ensure your MTD permissions are active in both QuickBooks Online (QBO) and HMRC. In QBO, go to the VAT section and check the status of your MTD connection. Additionally, log in to your HMRC account to confirm your VAT account is enrolled for MTD.
 

For further guidance, I recommend reviewing this helpful resource: Fix MTD issues in QuickBooks (VAT and ITSA). It includes detailed steps and prerequisites to consider before troubleshooting.

If you have any other questions or need further assistance, feel free to reach out. We’re always here to help.