A modified re-buy is a situation where an organization or an individual buys goods that had been previously bought, but changes are made to the supplier. The purchase requires additional research or analysis to be conducted. Ideally, the buyer wants the modification of the terms, process and other relevant specifications.
In a modified re-buy, the "in supplier" becomes more cautious on protecting his account while the "out supplier" views it as an opportunity and strives to offer a better option in order to get new business. This type of transaction is less critical and requires a little amount of time since only modifications are made in the original transaction.