How to spot financial infidelity: The red flags your partner could be "cheating" on you.

Your partner has started getting weird on you. They’re dodging your questions, keeping you from looking at the mail and taking out large sums of cash without reason.

They could be cheating on you – but it might not have anything to do with another woman.

Financial planner James Trethewie – who just so happened to be one of the men vying for Sophie Monk’s heart on The Bachelorette last year – says these are all major red flags you’re a victim of financial infidelity.

Listen: Sexual psychiatrist explains to Mia Freedman exactly why it is that happy people cheat, on No Filter. (Post continues.)

The signs of financial infidelity

As James explains, financial infidelity covers any kind of spending or money issue a partner is trying to keep hidden, like credit card debt, gambling problem or even an addiction to Michael Kors handbags.

He tells Mamamia if you notice your partner doing these things, it’s time to worry approach them for a frank conversation about finances.

Weird behaviour.
Similar to romantic infidelity, secretive behaviour, inexplicable changes in routine, mood shifts or a noticeable (and again unexplainable) change in stress their level could all be signs they’re hiding something.

Big cash withdrawals.
“If you’re looking at your statements and you’re seeing big or frequent cash withdrawals and you don’t know what they’re for, it’s a sign something might be up,” James, who writes for Financial Planning Association of Australia’s newsletter Money and Life, says.

Iffy transactions on your statement.
Similarly, James says if you’re looking at your statement and seeing significant purchases that aren’t to Woolworths, Kmart, your local pub or anywhere else they normally spend their money, it could be that they’re buying some things they’re not telling you about.

Getting cagey when you try to bring it up.
If you question them about any of these purchases or withdrawals and they “get a bit funny about it” or try to change the subject without offering any real explanation for the spending, you could be looking at a guilty person, says James. “A good pickup would be their behaviour getting a bit weird and they’re trying to deflect the subject.”

Tries to keep you from checking the mail. 
On the other hand, you might not remember the last time you actually saw a bank statement. James says if your partner always seems to be the one who gets to the mailbox first or insists on being the person to check the statements, it should raise an eyebrow or two.

Letters from banks you don’t recognise.
“If you start seeing stuff in the mail from financial companies you don’t normally use or deal with that’s something you should ask about,” James says – it’s a sign your partner could have set up a bank account so they can make secret purchases without being caught.

Sets up a new credit card without telling you.
James says it’s important for communication about money to be open and honest in a relationship and things like whether to get a new credit card or not should be raised and discussed. The fact that they haven’t could mean something’s up.

What to do about financial infidelity

James tells Mamamia that if a married or de facto couple aren’t already having regular conversations about their finances, he recommends they start.

“So you set up a regular time to sit down and talk about your finances, maybe once a month, just to go over everything. You can talk about your assets, how you’re heading, how any debts are going, any savings, anything you’re saving for.”

“That’s probably a point where, if you’re noticing this stuff, that’s where you can bring it up.”

James also recommends creating some kind of savings plan if there’s a goal you both want to reach, such as a house deposit.

If, for example, you know one person is the type to spend everything available to them, it’s a good idea to set up a direct debit to a savings account on payday. The Barefoot Investor’s “buckets” method might also suit you.

Watch: Financially savvy couple David and Libby Koch share some advice on how to manage your money. (Post continues.)

However, if your partner’s secretive spending has become a problem you’re both struggling to handle alone, it’s worth reaching out to a professional, says James.

“If it’s to do with a problem like gambling or excessive spending maybe seek some professional [psychological] help as to what’s going on before it gets out of control,” he said.

“If it’s already in a place where you’re communicating well about it and you can make the right steps forward, but you just don’t know where to start, I’d encourage people to seek professional advice. Whether they see a financial advisor or a debt advisor about what they can do to get on top of things, I think that’s a good idea.”

James also recommends checking out free online resources like the Federal Government’s Money Smart website or the FPA’s Money and Life site.

Have you had a tough conversation about money? How did you handle it? Tell us about it in the comments below.

*James’ views are his alone and don’t necessarily reflect the views of Financial Planning Association of Australia or of his employer.