Seriously, if you are even beginning to think in the back of your mind that buying something is going to upset your wife when she finds out, doesn't that maybe tell you that you should at least talk to her before you make the purchase? My wife and I are very open about our spending habits. We are kind of forced into it as I am paid monthly, so at the beginning of each month, I pay all our bills, and then we use the remaining amount and her biweekly pay to stick some into savings and live off the rest of it for the month. So, random purchases aren't exactly common, though both of us never really say anything to one another if we buy something for around $20 or less. Anything more and we usually talk about it before we buy, and budget for it if its somewhat expensive. Not being open about finances and spending is really asking for trouble. Its just not a smart move. If you have to ask yourself or you are second guessing, the answer is yes, the wife will be mad, so talk to her before you do it. A simple 2 minute conversation could save hours of fighting and frustration.