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I've done freelancing work for a little over a year and by and large have been paid very reliably, with one notable exception. I've set up payment in stages with one of my clients, and the project is on hiatus while the client figures out what they wants next. I'm happy to put the project on hold, but I'm awaiting final payment, and I have been for several months. I've sent the client several emails. They responded to the first email with a vague promise of payment but have not responded to the next few emails, politely reminding him about the outstanding payment.
To complicate matters slightly, the client is the son of a family friend. I want to remain in good standing with him, but I also do wish to get paid in a timely fashion. I'm not sure how to push this issue without coming across as rude or abrasive. How can I confront him about the outstanding payment while remaining professional (and preferably, allowing him to save face)?