A marriage should have no secrets, especially financial ones. Isn't finances the number one cause for divorce? If you are ashamed or embarrassed of the purchases you are making with your credit card, perhaps you shouldn't be making them?

In turn, if you are using your credit card wiseley, for reasonable and tolerable purchases, what do you have to hide?

Yes but some how......Ethically you need to beware about the activity you perform and spouse must know about this.
However there must be cases as ; you think that your spouse make misuse of credit card and you got facts too, You have frankness enough that both of you use or check another activities without asking of.
But if you take this in a positive way then you must bring this in her notice and communicate with her before checking her credit card balances.

The act of checking on your spouse's credit card balance is neither ethical or not. Your motivation behind the act is what can be challenged on moral grounds. Are you checking it because you want to help her (i'm a guy) pay it off? Are you checking it because you think she's renting hotel rooms with another man? Are you checking it because you are over-controling and have to have knowledge of every little thing going on in your house?

Are you telling her you are checking it? Are you going to ask first? I do not believe that if you have serious concerns about her telling you the truth, and so you check her account because you don't trust her, that that would be an unethical thing. Though if you are wrong i think it would be a great chance to build some trust by confessing to her what you did and discuss why you doubted her. If you find out she is lying, i doubt you will feel a single pang of guilt for what you did.

Why don't you have dual/shared accounts?

My wife checks my balances, she doesn't hide, she'll straight ask me, "what did you buy here?"
It was a little invasive at first, but i know that i don't handle money well. She knows that, i told her that, and i've told her about all the over-draft charges and late fees i used to pay. So how can i blame her for checking. It's not because she doesn't trust me, but because she loves me and knows me well enough that i am absent minded about those things. If this is your case, check up on her and be honest with her about it. Support her if she has bad habits like i do, she'll appreciate it in the long run.

I do not believe it is ethical to check on your spouse's credit card balances. The reason it is unethical is that marriage does not give a person the right look at someone's finances without their consent. Any good marriage is based on trust. If someone is looking through your credit card balances without your consent, you can't trust them.

Of course its ethical to check on your spouses spending. In a marriage you are supposed to be working together and that means financially as well as other ways.

Financial/credit ratings involve both parties in a marriage. If your spouse's spending is causing your credit rating to go up or down, then you need to know about it.

God bless, J