I went on LTD in May 2024, my insurance company has given me an ultimatum to either come back in 3 months or to fill out a CPP disability application. Can they force me to? What are repercussions if I refuse?

The decision to return to work (or not) should be made between you and your doctors. The insurer cannot force you to return to work. That said, they may cut you off of LTD benefits in certain situations if you refuse to return. In those instances, you should contact a lawyer right away to go over your options for fighting the denial.

With regard to applying for CPPD, under most modern LTD policies, there is typically a requirement that you apply for CPPD (at least at some point), and if you don't, the insurer is permitted to deduct the CPPD you could have received had you applied and been approved. That said, I would need to see the terms of your specific policy to be sure.

If you do apply for CPPD, you should also look into applying for the Disability Tax Credit, since CPPD is taxable.