I've talked about this with my friends who live in relationships, and I was surprised how different approaches people take with splitting the bills, especially with groceries and other smaller stuff. Some of my friends have a system where other pays for groceries, and the other the rent/water/electricity monthlies. Some split the monthly bills, and just take turns going shopping et al. Personally, me and my girlfriend are keen to split everything: we save all the receipts, and mark up the payer and if one of us bought something the other doesn't use. Roughly once a month we gather all the receipts and calculate the balance - it takes about 10 minutes, but we figure it saves us from quarreling over money, especially as we are both students, and live on very limited income. What kind of approach you guys have?