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Why you fight: Maybe one person takes on more of the fixed expenses, like the mortgage, car payments and insurance, while the other partner pays for the variable expenses such as clothing, food, transportation and household items. Variable expenses can’t be predicted, so one partner can often wind up “in the hole.”

How to stop: Having separate accounts doesn’t have to be a source of conflict. A good rule of thumb is to divvy up the monthly expenses based on the percentage of income each person contributes to the household. For example, if one partner has an annual salary of $50,000 and the other makes $25,000, the partner who earns $50,000 can contribute twice what his or her spouse does.

The bottom line: It’s a good idea to sit down once a month and talk about what’s being spent and on what, so each person is aware of the entire financial picture.