How to prove Ontario Residency?

I am a Canadian citizen who moved to the US 5 years ago to complete a masters degree. Since graduating, I have been working in the states on a TN visa. My husband and I (he is also Canadian, working on a TN) would like to move home asap to be with our aging parents.

I was able to find a job as a stop-motion animator with the animation studio I worked for before moving to the states.
They would like to hire me, but can only hire “Ontario Residents”, due to the film tax credit they receive.

I have been trying to find out how I become an Onatrio Resident again, but have not been able to find information for returning Canadians. Can you tell me what I need to do and what the timeline is?

Many thanks,
Beatrice

Just file the tax? or after filling the tax and then get the notice of assessment? they both are different, can u please elaborate on this?