Q: Someone earns a lot of money (as business profit or rent deposit) just before the end of khums year. Can he consider a separate khums year for it or he should pay khums on them at the end of his khums year?
A: It is like other earnings of the same year. He should pay khums on what remains unspent on ma‘ūnah*. However, the money one takes as rent deposit from a tenant is ruled as a loan which is not subject to khums.
Ma‘ūnah: what one needs for the expenses of his life and that of his 'dependants', e.g. for food, clothes, house, etc.