When you're trying to manage the family finances, you need the full support and cooperation of your spouse. When your spouse is bad with money, it's up to you to take the steps to protect your family financially.
Assess the situation. Is your spouse bad with money because they were never taught any better or do their financial problems stem from something deeper? Is their problem chronic shopping and spending or do they have a more serious problem, such as a drug or gambling addiction? Before you can begin to fix the situation, you have to look at what the real problem is and whether or not you can or even want to try to fix it.
Once you've identified the problem, you need to decide what can be done to try to fix it and if you even want to try. Ultimately, it's going to be up to your spouse to make the necessary changes to their behavior so you have to know going in what you can tolerate and what's a dealbreaker for you.
If you're willing to try to fix the problem, the first thing you need to do is sit with your spouse and try to talk to them about your concerns. Talking about money is very likely going to be uncomfortable, and your spouse may react defensively and be unresponsive at first. Resist the urge to blame all of your money problems on your spouse alone. Unless you've only recently discovered the depth of your joint money troubles, then you have some responsibility in this too.
Once you've got a dialogue going, then the two of you together need to sit down and make a plan for repairing your finances. The key in this is to make sure that you are participating equally. Your spouse does not want to be treated like a child any more than you want to be a parent figure. You need to have a plan for budgeting, saving, getting rid of debt, and setting longterm goals. Together, decide on how you will reward yourselves for accomplishing your goals.
If your spouse is unresponsive, then you may want to suggest counseling. Having a third-party take a look at the situation may make it easier for him or her to voice their opinions without feeling attacked. If they are still unwilling to talk about your marital money problems, then you need to decide if the marriage is worth saving.
If you can't reach your spouse but can't leave the marriage, take steps to prevent them from accessing money that is to be set aside for bills, groceries, savings, etc. If they are responsible for paying a portion of the bills, set up an auto-draft each money to move the money automatically out of their account. Do not give them access to your credit cards or open joint credit or cosign a loan for them.
Don't talk down to your spouse. If you want them to act like an adult, then you have to treat them like one. Have regular financial meetings, where you jointly discuss and make decisions regarding your finances. Making your spouse a part of the process rather than taking away all financial control will make them feel that they are participants rather than observers.
Things You'll Need
Recent copies of both you and your spouse's credit reports
Recent copies of all bank statements
Recent copies of all the bills
If your spouse's spending habits are due to drugs, alcohol, etc. and they are unwilling to seek counseling, then you really need to decide how far you're willing to go to save the marriage, particularly if you have children.