My wife just learned that some people do this. She similarly had no idea this was a thing and doesn't quite understand how it works.
1. Paychecks are auto deposited into separate checking accounts.
2. Recurring expenses are paid from one of those accounts; it doesn’t matter which one. There is no ledger to determine if each party pays their “share.”
3. Most payments are automated and paperless, coming from whomever bothered to set up the account initially.
4. Non-automated bills or expenses are paid when they occur, by whomever happens to get the mail/see the bill/grab their credit card first. We might discuss payment logistics for larger expenses, but usually we just do it.
5. Same goes for going out to dinner, etc.
6. Nobody scrutinizes the other partner’s spending, and we aren’t concerned about a “budget.” We’re extremely fortunate in this regard, as our income individually is more than enough to support both our spending habits and save for retirement. Since we both earn roughly the same, the second salary is effectively insurance, if something goes financially awry.
7. I don’t “hide” money/expenses from my wife, and I assume she’d say the same.
Make sense?
ETA It’s actually easier than creating and maintaining separate + joint accounts, apportioning expenses and worrying if some arbitrary level of “fairness” is achieved.