Discount summary
If you deal with customers that have large accounts, always document the reasons why you gave a particular discount on that specific product or service.
It gives you information on whether the discount should be carried forward in the future, whether it was a “special” just for an old friend, whether the order was very large (large at the time for your young start-up), or any one of a myriad of other reasons.
It also gives you information on whether you can combine a discount by bundling with another service.
Plus, the sales people that deal with the account long after you are gone will thank you when suddenly that old customer is saying “Yeah, but Mike always gave me 30% off every order.”