If your clients are not paying on time the first step to make sure that you have taken is to have a proper accounts receivable program in place. A proper accounts receivable program starts with a clear invoice that is timely mailed to your customer.
It also includes regular reporting and tracking of clients who are past due and includes a series of follow-up steps when a client is late. Following this sort of program is the most efficient and cost-effective way to make your clients pay on time but after following your program at the end of that program should be a step that says we are going to engage a collection attorney.
At that point the collection attorney takes over. If you follow the previous steps, which also include having a properly drafted contract laying out the payment responsibilities and the responsibilities of the parties, that gives your collections attorney the best chance of enforcing the agreement and collecting your money and should you have to sue, provides the best foundation for winning that lawsuit.