After a tax/vat return has been mark filed, is it possible to un-file it?

Hello there, pankhaniaco.

Thanks for reaching out to us here, but I have to direct you to contact our Customer Care Team. This is because the process of unfiling the tax return is carried out by our back-end support. 

When contacting our live agent, make sure to provide the following information:

• QuickBooks Online Company ID.
• Which tax filing period you wish to unfile.

Then, follow these steps:

1. Click the Help icon located in the upper right-hand corner.
2. In the Help window, click the Contact Us button located at the bottom.
3. Enter your question and click Let's talk.
4. Choose either Start a chat or Call us.

If you have the new QuickBooks Assistant help update, you can follow these steps:

1. In your QuickBooks Online account, go to the Help > Assistant.
2. Type Talk to a human and proceed with I still need a human.
3. Click the Contact us link.
4. Select either Messaging or Callback.

I'm also adding these articles for more details:

• How to unfile VAT/GST
• File your tax return and record tax payment in QuickBooks Online

Should you have other concerns about your QuickBooks Online account, please let me know in the comments below. Stay safe!