Budgeting system where two people agree to pay a % of the total expenses that relate to both parties (eg., 50%/50%). At the end of the month, the amount each has paid towards the total expenses is compared to the amount they were supposed to pay based on their %, and the difference is paid back to the partner that paid more than their % was decided to be.
Eg. If I paid $700 for rent, and my partner paid $300 for food, the total expenses were $1000. But I paid 70%! Therefore, to make sure we both paid an even 50/50, my partner would have to pay me back 20% (or $200). You get to choose what % each partner should pay!