Can a new owner serve an N12 to move in a family member shortly after closing on a tenanted property?

Yes, a new owner can potentially use this process to end a tenancy so that themselves or a qualifying family member can move in, but this notice is subject to the same strict requirements as any other purchaser's or landlord's own-use notice under the Residential Tenancies Act, 2006, including proper notice, the associated compensation obligation, and a genuine, followed-through intention to actually occupy the unit. Buying the property does not relax any of these requirements.

Because the tenant can dispute the notice and, separately, can later apply to the Landlord and Tenant Board if they believe the notice was not given in good faith, using this shortly after closing carries the same risk of scrutiny as it would for any other landlord, arguably more so if the timing looks like it was planned around the purchase from the outset. A new owner going this route should be prepared to demonstrate a genuine intention, follow through on it, and understand that the timeline for actually achieving vacant possession is not guaranteed to match their own plans. Speak with a lawyer before serving this kind of notice to make sure it is done correctly.