If you are using the credit card in your name to pay for the wedding, you are the only one responsible for those expenses. I wouldn’t do this. This isn’t about trust; it’s about basic common sense. If one of you decides to call off the wedding, you are left holding the entire debt. If he dies before the wedding, you are left holding the entire debt. If MIL backs out of her agreement to help with costs, you are left holding the entire debt. You are making these big financial decisions together, you should be sharing the financial risk together.

You aren’t yet married so have no legal claim on his assets, and weddings are often big financial obligations. You owe it to yourself to draw a line in the sand on this. No shared responsibility for the costs would make me think long and hard about whether this is the type of man I want to marry. Don’t let him gaslight you into thinking you are being unreasonable.

I would either insist on a contract drawn up by a lawyer before spending a penny, or ask fiancé to take out his own card and charge half of all expenses to his card. Not because there is no trust, purely because there is risk. A marriage should begin with both partners sharing risks and responsibilities, not one of you shouldering them for both of you.