Infidelity and family law: what to do if your partner is cheating

Shocked, betrayed, confused, and angry. These are the emotions that hit you first when you discover your partner is cheating. Finding out your spouse is having an affair is devastating; it often signals the shattering of the future you thought you were building together.

But while the emotional toll is heavy, the financial reality of separation needs immediate attention. If the trust is gone, your priority must shift to protecting your future and your assets.

Worried about your assets?

If you’re separating due to infidelity, your financial security is the priority. Don't wait for things to get messy.

Get in touch with our family lawyers to discuss protecting your share of the relationship property.

Should you stay or should you go?

There is no right or wrong response to a partner’s infidelity. Whether you aim to salvage the relationship through counselling or decide it is time to move on, there is work to be done.

If you decide to end the relationship, you need to look beyond the heartache. There are legal, financial, and practical challenges to navigate immediately—specifically regarding relationship property and care of children.

Does cheating affect who gets the house and money?

This is the most common question we get asked. In New Zealand, the law regarding the division of assets is generally "no-fault."

There is a misconception that if a partner cheats, they will be "punished" by the courts, or that the innocent party will receive a greater share of the assets. The reality is that adultery does not automatically alter the equal sharing rule under the Property (Relationships) Act.

However, there are three critical exceptions where the "50/50" rule might change.

1. The "Financial Infidelity" Argument (Dissipation of Assets)

Did your partner spend significant relationship funds on the affair?

• Relationship Debt vs. Personal Debt: If your partner took out loans or racked up credit card debt to fund trips, hotels, or gifts for someone else, we can argue these are personal debts, not relationship debts. You should not be liable for half of the debt they created to cheat on you.



• Dissipation of Assets: If they have deliberately run down your joint savings or sold assets to hide money, we can seek to have that value "added back" into the pool before division, ensuring you aren't short-changed.

2. Economic Disparity (Section 15 Claims)

This is the most powerful tool for spouses who sacrificed their career for the family.

If you stayed home to raise children while your partner built their career, they are leaving the relationship with a higher "income earning capability" than you. Under Section 15 of the Property (Relationships) Act, the court can award you a lump sum compensation to address this imbalance.

• Example: If your partner earns $150k and you earn $40k because you’ve been out of the workforce for 10 years, a 50/50 split of the house might not be fair. We can fight for a larger share (e.g., 60/40) to balance the scales.

3. Trusts are not bulletproof

A common threat we hear is: "Everything is in a Trust, so you won’t get a cent." This is rarely true. New Zealand courts have cracked down hard on "illusory trusts" or trusts used to defeat relationship property claims. If the trust was effectively treated as your partner’s personal piggy bank, we can often "bust" the trust or claim compensation for the value locked inside it.

The "Psychological Abuse" Factor in Custody

While infidelity itself doesn't usually dictate custody arrangements, the behaviour around it can.

Under the Family Violence Act 2018, psychological abuse is recognised as a form of family violence. This can include:

• Gaslighting: Manipulating you into doubting your sanity regarding the affair.

• Coercive Control: Isolating you from support networks or controlling finances.

If your children have been exposed to this conflict, or if the psychological abuse raises safety concerns, this becomes a critical factor in Parenting Orders. The court’s first priority is the safety and wellbeing of the children, not the "rights" of the parents.

Why you need legal advice immediately

Trying to negotiate a separation while you are grieving an affair is dangerous. Emotions run high, and guilt or anger can lead to impulsive decisions—like moving out of the family home too early or agreeing to a financial split just to "get it over with."

Here is why you need a lawyer in your corner:

• Objective Guidance: We stop you from making decisions based on anger or sadness that you might regret financially later.

• Protecting Your Rights: We determine exactly what counts as "relationship property" (including Kiwisaver, businesses, and investments) to ensure a fair division.

• Negotiation & Mediation: We handle the difficult conversations with your ex-partner or their lawyer, keeping the process as non-confrontational as possible.

Next Steps

If you have discovered your partner is cheating, take a breath. Then, take action to protect your future.

At Weston Ward & Lascelles, our Christchurch family lawyers offer discreet, confidential, and frank advice. We work to get the best equitable outcome for our clients and their dependents through the least stressful means possible.

Contact us today on  03 379 1740 to make an appointment, or  learn more about Relationship Property division here.