Factoring is a great tool for accelerating cash flow; however, unless it`s non-recourse factoring, selling your receivables doesn`t get you off the hook for selling to clients who won`t pay within 90 days of date of invoice.
I think Roughstock`s 10/3 comments are on target. Your customers are taking advantage of you and there are steps you can take to get the relationship back on track.
I`ve written postings about this issue on my blog - check out my 8/28 posting (Fire Your Customers - A Second Opinion) and my 8/30 posting (Are your Customers a High Credit Risk?). Don`t hesitate to contact me if I can be of any assistance.