Below is my experience:
May 2019 - Moved to Canada from US in work permit. Did not export the car and temporarily imported the car to Canada. ServiceOntario took my original US title.
May 2022 - Became a Canadian PR
Dec 2022 - Moved back to US for work reasons. Drove the car to US with Ontario number plates. The car was parked in my US home as I was using another car.
September 2023 - Moved back to Canada. This time know I should permanently import the car to Canada. So I started to prepare for exporting my car from US. I found my US title was still active with the state where I resided before moving to Canada in 2019. So I applied for a duplicate title from the state and received it by mail. Next, I used a customs broker's help to get my ITN.
I drove to the US border and had some trouble finding the U.S. Vehicle export office as my Google maps went crazy. But one gentleman stopped by and helped me find the U.S. Vehicle export office. In the office, I was questioned on why I (temporarily) imported the car in Canada without exporting the car from US in the first place. I apologized and informed the officer that I didn't know the process. I was fortunate that the officer was lenient and stamped my car as exported.
Next, in the Canadian border, I was again questioned on my purpose of visit to Canada. I explained that we are moving back to Canada and I am already a PR. The officer asked if the Car is in the list of goods that I am importing to Canada. I explained the whole story to him. They sent me to the customs office and made me fill a new Form 1. Now, I need to take my new Form 1 to Service Ontario and see what they say....
My advice:
1) Like
aruns1494 mentioned above, try to export the car from US before you import Canada. This will avoid a lot of hassle.
2) If you are returning to US to settle, You are allowed to keep the car in US with Canadian number plates for only 30 days in most states. So try to get US plates within the allowed time period.