You can sell a property with a tenant in it at any time. What you cannot do is sell it vacant just because you would prefer to, and the gap between those two things is where sellers get into trouble.
What does not change
Selling does not end a tenancy. The buyer takes the property subject to the existing lease, at the existing rent, on the existing terms. Your tenant keeps every right they had the day before you listed.
Showings
Twenty-four hours' written notice, stating the reason and a time between 8am and 8pm. Every time.
Your tenant does not have to leave during a showing, and does not have to tidy, stage, or make the place presentable.
You cannot use a lockbox for unaccompanied access without the tenant's agreement.
Open houses are not covered by the entry provisions in the way individual showings are, and running one over a tenant's objection invites an interference application.
A tenant who is on side is worth a great deal of money to you, and a tenant who is not can quietly cost you the sale. Talk to them before the sign goes up. Agree a showing schedule that works around their life, consider a rent credit for the marketing period, and be honest about what is happening. It is cheaper than the alternative and it is also the decent thing to do.
What you can and cannot promise a buyer
You can
Sell with the tenancy in place. Provide the lease, the rent roll, and the deposit details. Agree that the buyer will assume the tenancy. Ask your tenant whether they would accept a mutual termination on an N11, and pass on their answer.
You cannot
Guarantee vacant possession you have no lawful means to deliver. Only a buyer who genuinely intends to move in themselves can require an N12, and you serve it on their behalf. If the tenant does not go, you may not be able to close.
Where a buyer in good faith requires the unit for their own use or a close family member's, you serve an N12 on their behalf with at least sixty days' notice, ending on the last day of a rental period. Today that also requires one month's rent in compensation to the tenant.
If the buyer never moves in, or re-lists the unit at a higher rent, that is a bad-faith eviction. Maximum fines under the Act doubled on 1 July 2026 to $100,000 for an individual, and the Board can order substantial compensation on top. Do not serve an N12 for a purchaser whose intentions you doubt.
Selling with a tenant sits on top of the Residential Tenancies Act and the penalties are real. Take advice from a paralegal or lawyer before serving anything.