How do I force T4 filing for a company that ceased operating?

For these filings, QuickBooks Online doesn't generate an XML file for electronic uploading. Instead, you can preview and print the forms to paper and file them directly with the CRA.

Please know that when you close a business, you must file your T4 forms within 30 days.

Additionally, you can refer to this page for more information: Prepare and submit T4 slips and T4 Summary in QuickBooks Online.

Let me know if you have other concerns.