Mythical accounting of quid pro quo within a relationship, whereby one partner accrues credits by performing good deeds or chores and/or enduring suffering.
The theory is that this good will can be built up and then cashed in for favours at a later date.
This balance of reciprocity does not, in fact, exist. At best there is probably a 6 hour window of opportunity to make the most of any benevolence See "Brownie Points"