In a perfect world, clients would always pay on time and in full. However, over the course of a graphic design career, it is almost inevitable to come across late paying clients.
The first step to dealing with a client not paying on time is to contact them or to resend an invoice. A missed payment may simply be an oversight. A phone call or email reminder will often do the trick, with the invoice attached again to b sure they know what is owed. At this point, it is up the the designer if a penalty should be applied. This may depend on the history with the client... if they pay on time every month, it is probably best to give them the benefit of the doubt and start with a simple reminder.
It is also an option to charge late fees. Late fee policies should be clearly written in the contract, so the terms are spelled out from the beginning of the project. A small percentage penalty (even 1%) per month can help encourage on time payments, and make your company some extra income in the case of late payments. Again, whether or not you charge a late fee may depend on the relationship with the client, or you may wish to charge them no matter what, as long as the client knows the policy.
After several reminders, you may wish to take further action. If the client has been honest about their situation, you can work out a payment plan so you receive the full amount over time. If you are ignored or are given excuses, it may eventually be necessary to contact a lawyer. The best way to make sure you are eventually paid, even with legal assistance, is to spell out the terms and amounts of the project payments in a signed contract at the start of the job.
