Moved out from primary home to rent it, living in Ontario. Need to inform CRA, which form do I need to do this?

[daxabenp]

Bought a house last year for yourself, its been one year. Now decided I want to rent it out and move to another house that I am looking to buy.

How do I notify CRA that the first property I bought last year is no longer my primary residence and will be renting it out?

Which forms do I need to do this.

[TurboTaxKim]

There are special rules to consider when you convert your Principal Residence to a rental property. 

When the property use changes from personal-use to income-producing, the deemed disposition can result in a Capital Gain. Any gain resulting from this deemed disposition may be eliminated by the principal residence exemption (PRE) if the property has always been the taxpayer's principal residence. 

The following CRA information describes this election in greater detail and the letter you should send if you choose the election.

https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-re... 

As for determining the Fair Market Value (FMV), you can use the Property Assessment, compare like properties in that area, or (the most accurate way and CRA accepted), have an actual "Property Appraisal" done.