Don't ambush them with a sudden fee hike. This allows you to receive instant feedback from your clients about the planned hike. Most of all, don't give the impression that you're raising your rates in desperation. State when it will go into effect, and briefly inform your clients why you must take this action. Many IPs raise their rates gradually and without risk of losing existing clients by first billing only new clients at the higher rate.
Old clients pay the old rate.
Once you have enough clients paying the new, higher rate, you can safely tell the old clients that you're raising your rates. Your rates are raised. If your clients balk, immediately sit down with them and review what you've done for them so far, suggests Popovich. Ask if they're satisfied with your work. Inquire whether there are other tasks that you can do for them.