Hi Akman Construction,
In QuickBooks Desktop, the file name for T4 slips is set by default as .xml. I encourage you to contact our QuickBooks Desktop support team at 1-833-317-2226. They'll have the ability to work with you in real-time and look further into this from their end, so you can file your T4 slips without delay!
If you have any other questions or concerns, feel free to reach out again. We would be glad to assist!
