when can my client "patent pending" on his products?
It tells others that you have applied for a patent: you can describe your invention with a “patent pending” status when you have a patent application currently pending before the Patent Office of that country in which you want to promote your product with that status.
The “patent pending” statement, among others,
a) tells potential investors and business partners that you have taken steps to protect your invention
b) warns your competitors that they should think twice before copying your invention because if your patent application issues as a US patent, then you could sue them for patent infringement
c) creates a mystic aura around your product
Please watch my "Motives For Filing A Patent Application" course here
for more motives to file a patent application.