It causes more rows than sex and household chores and is often cited as one of the main causes of divorce. At its least harmful, it can lead to minor rows and bickering. At its worst, it is on a par with infidelity, causing a breakdown in trust, growing resentment and sometimes irreparable damage. What is it? Money - or to be more precise, the spending and saving of it. According to numerous surveys, money really has the potential to be the root of all evil when it comes to married bliss. A Canadian poll showed 86 per cent of couples admitted money caused tension in their relationship, with 48 per cent saying it was spending rather than debts which caused the most conflict. A similar survey of 1,000 British couples found that one in four couples even argued about finances while in bed. Hong Kong financial adviser Pam Bradley says changes in women's role in the family and the workplace had made money matters far more complicated for modern-day couples than it had been for their parents and grandparents. 'It is a lot more difficult today. You still get that traditional scenario where the man is the breadwinner and manages the finances but there are so many different situations as well,' says Bradley, vice-president of financial advice and investment company ipac. 'Every couple is different. I have met couples who are adamant they will share everything and all their money goes into a joint account. Then you have couples who choose to keep everything separate. 'In the traditional Hong Kong family, it is not unusual to still see women looking after the domestic finances while the man pays for the majority of things and looks after the wealth,' she said. 'With expat couples, you tend to get a bit of mixture. Those on their second marriages tend to keep their finances very separate. They may be very much in love but because of the bad experiences they've had in their first marriages, they want to keep things separate.' According to Hong Kong relationship therapist Julie Gallinat, the potential for conflict exists because how each person thinks and behaves with regard to money is influenced by the values, rules and beliefs they adopted from their own family and culture. 'In addition, we carry into adult relationships wounds or hurts that we experienced as children and teenagers with regard to money. We also we carry defensive strategies that we developed along the way to deal with and avoid these hurts,' says Gallinat, who runs pre-marital courses which cover dealing with joint finances. 'For each person, these values, rules, beliefs, wounds and defensive strategies can all vary greatly ... and there is potential for disharmony.' So how can couples avoid money becoming the thorn in the side of a rosy relationship? What they should not do, say Bradley and Gallinat, is bury their heads in the sand and hope it will sort itself out. Bradley believes the best survival plan for a new couple involves adopting an approach which mixes both separate and joint lives when it comes to their finances. This involves setting up a joint account to cover day-to-day expenses (food, electricity, rent), large expenses (holidays) and for joint saving goals (house, wedding, retirement), and then separate accounts for each couple so they have their own money to spend as they wish. 'If you go for a completely joint approach, it can get very messy. You don't know who is spending how much until you go to the bank and there is nothing in there and by then it is too late,' she says. 'The flip side is to lead completely separate lives. But then you have no idea what your partner is doing until all of sudden they come to you and say, 'I am so sorry but I have maxed out three credit cards and I need some help'.' 'By keeping your finances totally separate, you are not able to help each other out. A mixture of the two is the ideal. It is not perfect for everyone, but it is a good step for a lot of couples.' If you adopt the mixed approach, the next important step it to sit down and work out what expenses are joint and what should be considered separate, and how much each partner should contribute to the joint account. 'This is definitely a conversation you need to have when you are in a good mood and being very kind to each other,' says Bradley. 'If you both earn the same amount of money, you might decide to put the same amount into a joint account. But if you earn different amounts, you have to work out what is good for you as a couple. Is the person who earns more money happy to contribute more into that joint account? Or do they contribute the same and leave the lower-earner with less in their personal account? It really depends on the couple.' Bradley says failure to get it right can cause resentment which is why talking about money is important. Good times to first broach the subject, she says, are before a couple move in together, decide to get married, or when they commit to a joint goal - even if it is just a holiday in Thailand. 'It is never too early to get an understanding of how your partner spends and saves,' she says. 'Most couples are two very different people who have two very different styles in their approach to money. 'If you have worked those issues out from the start then you are less likely to have arguments about money down the track. You will be able to understand each other's perspective better and hopefully come up with solutions.' Gallinat agrees, saying failing to communicate over money can result in what she calls 'financial infidelity'. 'This manifests itself in a wide range of behaviour such as failing to be open about your finances, lying about how much something costs or hiding purchases, holding secret savings accounts or stashing money away, revenge spending, playing the stock market without the partner's knowledge and even buying to fill an internal need,' she says. 'Couples should definitely talk about money preferably in the pre-marital or pre-cohabitation stage of the relationship. An indicator of a couple's success with respect to money is the degree to which they support each other's dreams.'