If you qualify for the First Time Home Buyers tax credit (**see qualifications below), and purchased the home in 2017, you are unable to claim the credit on your 2018 tax return (filing in 2019).
You'll need to make an adjustment or ReFile the 2017 tax return to reflect this credit. Here's how to go about doing so:
https://turbotax.community.intuit.ca/replies/2647992
**CRA states that you qualify for this credit if:
- you or your spouse or common-law partner acquired a qualifying home (1)
- you did not live in another home owned by you or your spouse or common-law partner in the year of acquisition or in any of the four preceding years (first-time home buyer)
(1) A qualifying home must be registered in your or your spouse's or common-law partner's name in accordance with the applicable land registration system and it must be located in Canada.