If a party owes a number of payments to another, payable on different dates, it may like to pay a single lump sum payment in lieu of a number of payments such that there is no loss or gain to any party. The procedure of finding such a date is called equation of payments and the date found is called average due date.
Bills of Exchange
A bill of exchange is an instrument in writing, an unconditional order signed by the maker directing to pay a certain sum of money only to or to the order of a certain person or to the bearer of the instrument. The bill is written by the seller (creditor), called payee, to the purchaser (debtor), called drawee.