Mirror Wills feel safe, but they can put your children's inheritance at risk

Quick summary: Mirror Wills are two separate Wills, one for each partner, that reflect each other's wishes, typically leaving everything to the surviving spouse, then to their children when the second partner dies. They're popular because they're straightforward and cost-effective. The catch is that they're two entirely independent documents. Nothing legally stops the survivor from making a completely new Will after the first death, and that's exactly where families can lose out.

For most couples, a Mirror Will is a perfectly sensible starting point. Each partner gets their own legally valid Will, tailored to their own circumstances, that happens to say broadly the same thing as their partner's. It's affordable, it's easy to understand, and for many families it works out exactly as intended.

It rarely happens out of malice. Life simply moves on, and a Will written years earlier no longer reflects where the surviving partner's life has gone.

• Remarriage. The surviving partner remarries, and under English law, marriage automatically revokes an existing Will unless it was specifically made in contemplation of that marriage. Without a new Will, the estate can pass under intestacy rules to the new spouse, not the children from the first marriage.
• A new Will favouring a new family. Even without intestacy, a surviving parent may choose to rewrite their Will to include a new partner or stepchildren, sometimes leaving the children from the first relationship with far less than either parent originally intended.
• Care costs. If the surviving partner later needs residential care, the full value of the estate, including what was meant for the children, can be counted in a means-tested care assessment and used to fund care fees.
• Simply changing their mind. Even without a new relationship, family circumstances change, and a surviving parent is legally free to favour one child over another, or leave assets elsewhere entirely.

We've spoken with families who assumed their parents' Mirror Wills guaranteed an equal inheritance for all the children, only to discover after the second parent's death that a later Will, made after remarriage, had changed everything. By the time anyone finds out, there's often very little that can be done.

The good news is that this risk is entirely avoidable, and it doesn't mean giving up the flexibility a Mirror Will offers. Instead of leaving everything outright to your spouse, each of you can build protection directly into your own Will using a trust, so a share is locked in for your children immediately on the first death, regardless of what happens afterwards.

A Property Protection Trust ring-fences your share of the family home. Your surviving partner can typically continue living in the property for the rest of their life, but your share is protected for your children, safe from a later remarriage, a new Will, or a means-tested care assessment.

A Nil-Rate Band Discretionary Trust does the same for cash and other assets, using your available Nil-Rate Band (currently £325,000, until April 2030) to secure a share for your children without creating an inheritance tax problem for your spouse. Trustees can be given the flexibility to consider your spouse's needs too, guided by a letter of wishes you prepare, so it doesn't have to mean an all-or-nothing choice between your spouse and your children.

Many couples use both together, one to protect the home, one to protect everything else, giving genuine certainty that their children will inherit what was intended, whatever happens to the surviving partner's circumstances afterwards. If your existing Wills don't have this protection, it's worth having them reviewed.