But it turned out that he had a novated lease on the vehicle that came with a balloon payment at the end.

All of a sudden a considerable chunk of money was withdrawn from a joint savings account.

McCallum, now a director and adviser at Multiforte Financial Services in Sydney, was more than a little taken aback. It was the first time she had ever ventured into the world of joint bank accounts and having a partner raid (my words, not McCallum's) that account was not quite what she had in mind.

The problem was not so much having joint finances, but relying on assumptions about finances, rather than asking questions, says McCallum.

He had made assumptions the loan wouldn't bother his girlfriend. McCallum had assumed the car was paid for.

"You just have to ask the questions. If you do, you are less at risk of receiving nasty surprises," says McCallum.

Kellie Payne, of RI Caloundra, says: "If you don't know where the money is being spent, money can be spent on things that are not part of the partnership and you have nothing to do with them. That is a worry."

The other advantage of asking questions and knowing what money comes in the door and what goes out is that you are prepared for any event. Unfortunately, nasty events can happen. Through death, divorce or separation, women can end up living on their own.

"You never know what is going to happen," says Dominique Bergel-Grant, of Leapfrog Financial.

Payne says: "It is really important that people know where the money is coming from and where it is going. I do find it a problem if women don't know."

McCallum says: "It demystifies the whole thing if you get involved. It all becomes more familiar."

McCallum has a great suggestion on this front. She recommends drawing diagrams that show where the income comes from, including salary and investment income, and where it flows to, including mortgage or investment loan repayments, household bills, entertainment and living expenses, insurances, cars and other hobbies. It may sound like playschool, but McCallum is adamant it works.

Bergel-Grant has some other (proverbial) pearls of wisdom. Always understand what you are signing and understand what investments you are making. If this means seeking some professional advice, then do so.

Understanding investments is particularly important if your retirement savings are wrapped up in a self-managed superannuation fund rather than a large pooled fund run by a bank or industry fund provider.

Is the self-managed fund invested in shares? In property? In cash? What sorts of shares? Are they shares in high risk or low risk companies? If there is a property, does it account for a large portion of total assets in the fund?

Your financial future may depend on you having answers to these questions.

A cautionary tale

Natasha David knew early on, when her future husband suffered a psychotic episode, that he had mental health issues.

Knowing his struggles, David took control of the couple's finances, and later remortgaged the house to help him establish a real estate agency.

But when her husband died by suicide 10 years ago, days after she requested a separation, David found herself in a world of emotional pain, and financial responsibility.

"I was coping with grief, post-traumatic stress disorder and anxiety and still being strong for myself," says David, now 42.

With a mortgage and bills to pay, David returned to work after a week's bereavement leave.

Dazed with grief, she had to organise a funeral, wind up her husband's business, pay legal costs and deal with matters such as closing his superannuation account.

"You are at your least able to cope mentally and so all of a sudden you're pushed into doing these forms and things," says David.

A year after her husband's death, David decided she could no longer live in their marital home, and bought a city apartment.

But her first house took six months to sell at a decent price, and she had to pay two mortgages for six months.

Emotional support from family and friends after her husband's suicide was crucial. But David says it wasn't until she wrote a book about her experience, Marrying Bipolar, that she was able to let go of her grief.

She advises other women to understand their finances, "even if you think your marriage is still going fine … and your husband is happy and healthy".

Case study: Larissa Ham

The information in this article should not be taken as financial advice. Please consider your personal circumstances before making any financial decisions. Readers can also visit anz.com/women.