It's important to have open and honest communication with your spouse about finances, including how each of you spends money. However, the level of detail you need to know about your spouse's spending will vary depending on your individual circumstances and preferences. Some couples may prefer to share all financial details, while others may be more comfortable keeping some aspects of their finances private.

When considering how much you need to know about your spouse's spending, here are a few factors to keep in mind:

1. Your overall financial situation: If you and your spouse share financial goals and responsibilities, it's important to have a clear understanding of each other's spending habits in order to make informed financial decisions. This includes knowing about major expenses, such as mortgage or rent payments, car payments, and childcare costs, as well as smaller expenses, such as groceries and entertainment.

2. Your trust in your spouse: The level of trust you have in your spouse will also influence how much you need to know about their spending. If you have complete trust in your spouse's financial decisions, you may feel comfortable giving them more freedom and autonomy in how they spend their money. On the other hand, if you have concerns about your spouse's spending habits, you may want to have a more detailed understanding of how they're spending their money.

3. Your personal preferences: Ultimately, the decision of how much you need to know about your spouse's spending is a personal one. Some people may prefer to have a very open and transparent relationship about finances, while others may be more comfortable maintaining some privacy. It's important to discuss your preferences with your spouse and find an arrangement that works for both of you.

It is generally more effective to focus on fostering understanding and trust in each other's priorities, values, and objectives when it comes to finances, rather than keeping a close watch on every aspect of each other's activities.