Can I file T1 and report both a T4 from Ontario plus a T4 from Saskatchewan?

[RM4]

I work and live in Ontario but worked for 3 months in Saskatchewan last year (same employer). I got a T4 from ON and a T4 from SK. 

My understanding is that I only file one tax return and and report both T4 slips indicating the respective province as per the T4. I will pay Federal and Ontario taxes in my T1 and there is no need to file and pay taxes separately for the Sask T4 income. Please confirm.

[TonyC11 · Accepted solution]

You correct. It is your province of residence on December 31st that determines provincial filing.
Everything goes into the same T1 return, you cannot file twice.
You will pay Ontario taxes on all your income, and receive Ontario credits.