Review your credit history with your customers and analyze your record of continued extension of credit to slow-paying or delinquent clients. Generally, if they aren't paying in a timely fashion, action is indicated. You might want to calculate accounts receivable on a monthly or even weekly basis to quickly identify delinquent accounts. Sometimes a prompt phone call is all that is needed to encourage the customer take an early payment incentive or pay the bill. Once the discount date passes, however, that money is unlikely to come in until the last day of the non-discount period.
Some companies just like to abuse the terms because they can.
They go ahead and take the early discount but pay in 30 days instead of 10. There is no easy fix for this other than sitting the customer down and explaining that their actions are jeopardizing a good business relationship.