Who Pays When Couples Dine Together?
According to Modern Manners Guy, the key is to establish expectations early so there's no awkwardness or misunderstanding later on
When couples head out to eat together, the general rule is that each pair takes care of their portion of the bill. However, this can depend on the type of invitation.
Questions like "Would you guys like to join us for dinner?" and "Why don't we grab dinner together?" are a little ambiguous. So to be safe, always expect that each couple pays for themselves in these cases.
See also: Paying for Dinner
If you want to make it clear that this will be a special treat for your friends, you might say something like, "May we take you to dinner?" or "We'd like to buy you dinner." That way, your intentions are clear up front and there's no confusion at the end of the meal.
Even if you follow these etiquette rules, often the end of a couples datebecomes a discussion about who will pay. Asking the server for separate checks is perfectly appropriate -- just make sure you aren't asking for separate checks after you waited a moment to see if your friends would be buying your dinner. If there wasn't a clear expectation set up before the meal, it's better to default to splitting the bill instead of sitting around awkwardly waiting for someone to make a move.
See Also: How to Properly Split the Bill