Tax return for 25-26. New to MTD

Hi there, Andy. Error C55326 means HMRC is looking for the specific start and end dates of your business's accounting year. Since you've completed the assessments without issue, the error that shows up needs further checking by our QuickBooks Online Support team.

I suggest reaching out to them, as they have the necessary tools to check and determine what the next step will be. To contact them, click the Help (?) button > click Contact Us > Choose either Callback or Chat to speak with a representative.

If you need anything else related to QuickBooks, don't hesitate to reply here. We're here to help.