“… great. That payment arrangement’s ok with us so, if you’re ok with it too, then everyone’s happy. Don’t you agree?”
Regardless of what’s being said to you, if the person speaking to you ends with those words, the natural tendency for all of us is to say “Yes”. Don’t you agree?
Whether you just said Yes or No to my question at the end of that last paragraph is irrelevant; behavior analysis and cognitive psychology suggests that it feels much more comfortable and natural for us to say “yes” than to disagree and say “no” when asked something using those three words. Don’t You Agree? (did you just say “yes” again perhaps?)
So, whenever you’re seeking compliance or agreement with anyone (such as a slow paying client) use those words. My wife often uses them (when she knows I’m not really listening) and I’m told (often days later) that I agreed when we spoke about …. ??????. Gasp.