General information only — not legal advice. The difference between joint and mirror wills can have real legal consequences, and the right choice depends on your relationship, family and assets. This guide explains the general position only. If you are a couple planning your wills, get advice from a qualified New Zealand lawyer.
The short answer
Mirror wills are two separate wills — usually for a couple — that contain the same or similar terms. Joint wills are a single will document made by two people together, which is rare and generally not recommended in New Zealand. For most couples, the right answer is mirror wills (or simply two separate wills): each person keeps their own document, and each keeps the freedom to change it.
Mirror wills explained
With mirror wills, each partner makes their own will, and the two documents say the same thing — typically that everything passes to the other partner, and then to the same beneficiaries (often children) when the second partner dies.
The key point is that they are still two separate legal documents. Each person can change their own will, and one will is not legally tied to the other. In practice, couples usually update them together — but neither person is locked in.
Joint wills explained
A joint will is a single document signed by two people as their joint will. This is an unusual and legally complicated arrangement. The central problem is that a joint will can raise questions about whether it can be changed or revoked, because the two people made the document together and each may have relied on the other’s promises.
For that reason, joint wills are rare in New Zealand and most lawyers advise against them. They can create serious difficulties for the surviving partner, who may find themselves unable to change their will even though their circumstances have changed.
Key differences
In practical terms, the differences matter:
- documents — mirror wills are two separate wills; a joint will is one document;
- flexibility — with mirror wills, each person can change their own will; with a joint will, the arrangement may become binding or very hard to change;
- control — mirror wills keep each person’s estate planning independent; a joint will merges the two;
- administration — mirror wills are straightforward to administer; joint wills can create confusion about whose estate is being dealt with;
- risk — joint wills carry real legal uncertainty, especially for the survivor; and
- suitability — mirror wills suit most couples; joint wills are generally avoided.
Which one is right for you?
For most couples, the sensible approach is two separate wills — often mirror wills — so each partner is provided for, the same people benefit when the second partner dies, and each person retains flexibility if circumstances change.
A joint will is rarely the answer. If someone suggests one, it is worth understanding exactly what is being promised — and getting independent advice before agreeing to anything that could limit your ability to change your own will later.
When to get advice
See a lawyer before deciding how to structure your wills as a couple if any of the following apply:
- either of you has children from an earlier relationship;
- there are significant assets, a business or a trust;
- you want a will to be irrevocable or binding in some way;
- you are unsure whether your wills are actually mirror wills or something else; or
- either of you may want to change your will independently later.
The bottom line
Mirror wills give couples the same outcome with freedom and simplicity: two separate documents that protect each other and the same beneficiaries. Joint wills bundle those decisions into one document and create legal uncertainty that most people do not need. For the vast majority of couples, separate wills — mirror or otherwise — are the right choice.