Can I claim both the first-time home buyers' GST/HST rebate and the new housing rebate in Canada?

This answer covers Canadian federal tax law, which applies in every province.

Yes, if you qualify for both. The first-time home buyers' GST/HST rebate can be claimed in addition to the new housing rebate as a top-up. A buyer who fails the first-time buyer test may still qualify for the regular new housing rebate.

The two rebates interact. The new housing rebate is the lesser of $6,300 and 36% of the tax paid when the total consideration is $350,000 or less, and it phases out to nil at $450,000. The first-time buyer rebate for a home of $1,000,000 or less is the lesser of $50,000 and the tax paid, minus any new housing rebate. Between $1,000,000 and $1,500,000 it phases out, and at $1,500,000 or more it is nil.

Eligibility for the first-time rebate is stricter. The buyer must be at least 18, a Canadian citizen or permanent resident, and not have lived in a home they owned as a primary residence in the current calendar year or previous four years, and neither they nor their spouse or common-law partner can have received the rebate before. The agreement must also be signed after March 19, 2025 and before 2031, and ownership must transfer before 2036. Check your facts with a lawyer or accountant.