Would you pay back your SO

Would you pay back your SO for things that you were supposed to put money on? Like if you were getting an apartment and they put both of y'alls down payment or if you were supposed to buy the holiday pie but they did instead? (I'm just using a big and small examples) and would you expect them to pay you back? I personally think y'all are in it together and if y'all live together whether you're married or not it's y'alls money. Like you don't always have to ask to buy something I'm just saying. This was just a shower thought I had and was wondering what y'all thought.