It makes sense in a certain way for a husband and wife to split bills in this manner. However, if you look deeper into it, it doesn’t do a good job of distributing the incentives to make more money and get a raise.

For example, we have two earners, Susan and Tom who spend 4,500/month.

Susan nets $60,000 per year.
Tom nets $30,000 per year.

Their monthly breakdown would be:
Susan pays $3,000 per month. She is left with $2,000 per month to spend.
Tom pays $1,500 per month. He is left with $1,000 per month to spend.

This seems fair, as Susan makes double what Tom makes she pays and is left with double what Tom pays and is left with. But let’s see what happens based on two different scenarios:

#1 Susan gets a $10,000 raise (16.67%) in her annual net income. Expenses and Tom’s salary remain constant:

Susan pays $3,150 per month (5% more than before). She is left with $ 2,683.33 per month to spend (34.17% more than before).
Tom pays $1,350 per month (10% less than before). He is left with $1,150.00 per month to spend (15% more than before).

#2 Tom gets a $5,000 raise (16.67%) in his annual net income. Expenses and Susan’s salary remain constant:

Susan pays $2,842.11 per month (5.26% less than before). She is left with $ 2,157.89 per month to spend (7.89%% more than before).
Tom pays $ 1,657.89 per month (10.53% more than before). He is left with $1,258.77 per month to spend (25.88% more than before).

These scenarios show that while a raise for one is essentially a raise for both, the lower earner has less of an incentive to try to get a raise than the higher earner. This makes sense, because the higher earner’s raise is more than likely going to mean more money than would a raise for the lower earner.

Another issue with having a budget like this would be the lower earner being subsidized for larger purchases, introducing moral hazard into the relationship (“I’ll just go ahead and buy a new big screen TV since I’ll only have to pay 1/3 of it!)

The severity of these issues depends on the couple, their financial responsibility and their character (maybe they’ll both want to get a raise or they will consult with their spouse before buying that TV). But judging by some of the issues here on this thread, it looks like some people need to take these issues into consideration.

At the very least, you should be splitting the bills in proportion to your income; his share should be roughly four times yours.

I dated a married man once and refused to pay a dime until he started divorce proceedings. He is still married (four years later now) and really can’t afford his own life separate from his wife. He was making a lot more money than me and his wife, but because their separation was so painful, he spent a lot of money getting into the bachelor lifestyle, and now he and his wife are broke. I’m very glad I didn’t pay for anything, because it would have made it possible for him to have a girlfriend and a wife.

Had he gotten a divorce and gotten together with me, he would have had a ton of debt and had to pay alimony and child support, in which case I might need to subsidize our new relationship. Which is ridiculous if I had to pay for his mess.

I think you can see where I’m going. If you and your boyfriend can’t come to a more fair situation, get out and put the money into yourself. Heck, you and his wife should get together for drinks, you might become best friends!