My wife and I are in the “flush with liquidity so we don’t budget” category (DINKs in a reasonably-priced ‘burb with an income inside “the 10%”), but we ALSO have a standing policy to inform the other of any discretionary single-item over $50. ($50 was an entirely-arbitrary amount that hasn’t changed in our 14 years of marriage, despite our combined incomes rising by maybe 60% in that time.) I’m sure if one of us really wanted to, loopholes could be found (breaking a purchase down into smaller pieces, taking a liberal view of “non-discretionary, etc.), but if we had THAT problem, well we’d have something to fix in our marriage.

For us, this has worked well. It’s not that either of us have EVER said “absolutely not!” (not even once), but it CAN be a useful check on spending we’ll regret if you first have to come up with a way to explain proposed spending in a way that doesn’t sound stupid or you figure out you don’t have an intelligent answer to the first question that might pop in the other’s mind.

Our money is a hybrid. It goes into separate checking accounts more out of inertia than anything else. Most “discretionary spending” goes onto one of two credit cards, both of which are in my name. Monthly bills are an entirely-arbitrary split. (Mortgage and credit card out of mine, everything else out of hers, and every couple of months I manually draw each down to a couple $k ea. via a transfer to our retirement account at Vanguard.) But my wife does have a credit card under her name, as is our debit card, so she doesn’t have to feel like I’m spying on her if she wants to buy something without me knowing.