The problem is that if a working relationship is successful, the old adage of familiarity breeds contempt can often creep into the picture. An invoice that was once paid on receipt becomes one that gets put in a client's virtual "in-tray" - which is a liberty that should never go ignored, more especially if the work you've provided has helped improve a client's overall ranking.
How to deal with a reliable payer turned bad
It takes a lot of diplomacy and self control dealing with a once "good payer". After all, you don't want to lose their custom, but at the same time you can't afford to have any outstanding invoices hanging around. So, what do you do? How to you broach the subject with the client?
First: send a gentle reminder which can be politely penned 5 to 7 days of the date of invoice
Second: wait another 5 days and repeat the process without the word "gentle" in your reminder and asking if there was a problem with the work
Third: after a further 5 working days have elapsed and the client still does not respond or settle the outstanding invoice, it's time to take the gloves off and a dreaded "red letter" making sure you are quite firm by stating the invoice is "very overdue"
What to do if client turns shirty
At the end of the day if the client pays but gets a bit shirty over the reminders they've received, you have to sit back, swallow hard and make an even harder decision. You have to ask yourself if you really need to cope with that sort of stress? The sad truth is that you are the only person in a position to know whether you can afford to give up a "good client" that's turned into a bad or slow payer.
The problem is that our industry (virtual copywriting) is among those where clients don't think they should pay a deposit or the full amount for work they commission which is quite extraordinary. You don't get to go to a supermarket and buy a product you've never tasted before and expect not to pay for the goods until you're happy that it's what you expected it to be! With this is mind, the work you do for a client remains yours until it is paid for in full - as such my advice is to start a blog and publish any work that goes "unpaid" on it so at least a "good client turned bad or slow payer" who uses your unpaid copy would be risking Google's wrath for publishing duplicate content!