Note: Eligible tenants who rent and occupy an eligible rental unit under a rental or tenancy agreement together but are not married or in a common-law relationship with each other (roommates) may each claim their own renter's tax credit if all other criteria are met. 

Please read the following to see if they qualify to claim the credit.
B.C. renter's tax credit

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If you live with roommates, have been living in the rental unit for 36 months and have not claimed this tax credit before should you:

1. Note 36 months? Or only note 12? 

2. how do you then claim the previous 12 from 2023?

3. living with roommates do you claim the portion of the rent you pay or the entire cost of the rental unit?

4. Depending on the answer to 1 & 2, do you note the amount for the full number of months? 

@Tubott83 You would only claim the rent for the time you lived there during the tax year, so a max of 12 months. And you can only claim what you paid in total for the year, not the total that was paid by all the people sharing the unit. 

If you need to add the credit to your 2023 return, this TurboTax Canada FAQ tells you how you can do that using ReFile: I've filed my tax return. Can I still make changes?