Nia and Adrian shared everything, including finances. But Adrian had a secret.

Nia* thought her relationship with Adrian* was one built on trust, transparency, and shared goals. 

She knew he hadn't always been great with money — he'd been upfront about that.

Nia often initiated budget talks and money-planning sessions with Adrian, and she felt like they were on top of things. The couple spoke openly about money, and Nia thought they were on the same page. 

Watch: The number one cheating sign that everyone misses. Article continues after the video.

But with children to raise, they ran a tight ship. When Adrian stopped receiving bonuses, things became even harder.

"I asked him about it, and he explained that the way the business had been restructured meant bonuses were far less likely," said Nia. 

As a freelance worker, Nia tried to secure as much work as possible to help make ends meet. Bewildered by their predicament, she asked for a copy of Adrian's credit card statement. 

"He was extremely cagey, which was totally out of character. Instantly, something felt wrong," she said.

So, she asked for full access to his accounts. "Initially, he said 'no', which floored me, because we'd always been so honest and open with each other," Nia recalled.

With Nia unwilling to accept the secrecy, Adrian eventually agreed. It was then that Nia discovered Adrian had a completely separate financial life that she knew nothing about.

Discovering the truth.

"He had been receiving bonuses, but [had] them directly put into a private account," she said.

He'd also received a pay rise, but he had the difference paid directly into another account so Nia wouldn't notice. "There was also significant credit card debt I had no idea about," she added.

Nia was heartbroken, but what she discovered next was even more devastating. 

"Almost every dollar he was keeping for himself, instead of our family. [It] was being spent on gambling," Nia said.

"I was absolutely gutted. Putting aside how much our family needed the money, I couldn't rationalise how he could lie to my face. I thought we had something so much deeper. It turned out, I didn't know him at all."

What is financial infidelity? 

Hiding money from a spouse like this is known as 'financial infidelity'. The impact financial infidelity can have on relationships can be catastrophic.

On the surface, financial infidelity is about being dishonest about money. This can mean anything from hiding a bank account or secret debts, lying about an inheritance, to overspending behind your partner's back and having an undisclosed income or gambling in secret. At its core, though, financial infidelity is about the erosion of trust. 

"It can be all of those things," said psychologist Phoebe Rodgers. "Withholding information about past and current debts, and not disclosing the impacts of those — for example, past declarations of bankruptcy and limitations; non-disclosing financial gains or inheritances, and concealing spending, as well as overspending without any agreement to the expenditures.

"When you enter a relationship, it is built on trust, openness, transparency and honesty in order to create an equitable partnership; financial infidelity undermines the trust and stability and fairness of the relationship."

These days, it's easier than ever to be deceitful when it comes to money. Modern technology means bank accounts can be opened within minutes online, and income can easily be directed to multiple accounts, without anyone knowing.

While the financial consequences of the deception can be significant, leaving partners and children in vulnerable positions, it's not just about the money — it's also about the lies that come with it.

"Often lies are followed by more lies; and non-disclosure is deliberately withholding important information that would help your partner assess the health of the relationship and whether it is right for them," Rodgers said.

When the truth finally comes out, the damage can be huge. Partners who discover financial deceit often feel betrayed, hurt, and completely blindsided.

"Lies of this nature can be devastating; the betrayed partner feels deeply wounded and it rocks their sense of being able to trust others, as well as themselves," she explained.

"You don't feel valued, considered, or respected, and also emotionally unsafe."

When gambling is the secret

One particularly harmful — and common — form of financial infidelity is secret gambling. It's one of those issues that can fly under the radar for years, especially with online betting platforms making access easier and more private than ever.

Secretive gambling can drain bank accounts and destroy trust and stability. Partners may discover maxed-out credit cards, mystery withdrawals, or mounting debt with no explanation. It may also lead to further dishonesty, such as hiding income. 

According to Birches Health, signs of secret gambling in a relationship include unexplained financial gaps, increased secrecy about time and money, and a defensive reaction when questioned.

When financial infidelity becomes financial abuse.

While not all financial dishonesty is abusive, there's a point where it crosses a line — but it can be blurry. 

"Abuse is when there is a use of power and control over another," Rodgers said.

"If one partner is deliberately using money to control the other — such as keeping them financially dependent, withholding access to funds, or gambling away shared resources – that's financial abuse."

According to Jolene Ellat, CEO and founder of the Domestic Abuse Resource and Training (DART) Institute Australia, the difference between financial infidelity and abuse is intent. 

"Financial infidelity becomes abusive when one partner uses lies or secrecy about money to control or manipulate the other," Ellat said.

"For instance, one partner might secretly incur debt in the other partner's name or hide assets or funds to maintain control over the relationship's finances. This would be considered abusive due to the intent."

Elatt emphasises that women holding a safety fund is neither abuse or financial infidelity. 

"The key difference between financial infidelity and a safety fund lies in the intention, transparency, and purpose of the actions," she said. 

"A safety fund is a practical tool to ensure that the person has financial security in case of emergencies, separation, or situations where they need to leave the relationship for their safety or well-being. The idea behind a safety fund is often rooted in autonomy and empowerment, not deceit or control."

Can you overcome financial infidelity?

Like any type of betrayal, healing is dependent on the couple's values and ability to move on.  

That might mean financial counselling, therapy, or simply learning to talk openly about money again.

It may also mean recognising when the damage goes deeper — when the behaviour is part of a pattern of control or manipulation, rather than a one-off mistake.

For Nia, the lies about money indicated broader dishonesty, and she later discovered Adrian had used his accounts to hide sexual infidelity as well. 

"It was the most crushing experience of my life. I can't even describe the sinking feeling I endured, realising that this man I loved unconditionally seemed to have a double life. I honestly didn't think he had it in him to do this to anyone, let alone me," Nia said.

Financial infidelity isn't just about dollars and cents — it's about trust. And once that trust is broken, it will take more than a budget to rebuild.

*Names have been changed.

Feature image: Getty.