My Final VAT return is due to be submitted today but I receive the "taxReturnInvalidMTDEndDate" error message but no help on quickbooks pages etc - really is annoying

I'm glad you came here, eugeneeustace.

This error when submitting VAT return is often caused by outdated browser. We can try a few troubleshooting steps to resolve this. Let's start by using incognito browser to rule out the possibility of a web page issue. Private browsing doesn't store local files or cache.

• Chrome, press Ctrl + Shift + N.

• Mozilla Firefox: press CTRL  + Shift + P

• Safari, hold down Command + Shift + N.

If this removes the error, clear the cache of your regular browser to help QBO function more efficiently. Otherwise, you can use supported browser as alternatives.

If all else fails, I recommend contacting the HRMC. They can help review your user ID to make sure you can submit your tax return.

This link will route you to the HMRC website: https://www.gov.uk/contact-hmrc

Visit us again if you have other QuickBooks question. I'm always delighted to help. Have a nice day!