Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Flight Crew Instrument; Flight Crew Commercial; Flight Crew Multiengine
Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
I was present during loading and helped during the process. There were passenger bags and then a small amount of non-priority mail. Upon unloading the mail I discovered that one of the packages had a 'Lithium Ion battery' sticker. I took pictures of the package and showed them to the ramp staff. They said the mail was non-priority and came from the post office without any HAZMAT paperwork. I emailed the picture to someone in our safety department and he said there should have been HAZMAT paperwork associated with it.  I'm not sure what the process for HAZMAT shipments is and if packages like this are supposed to come from the post office with paperwork or not. But the ramp staff did not seem to know if the package required HAZMAT paperwork. So if it is supposed to have HAZMAT paperwork associated with it; something needs to be coordinated with the post office so that HAZMAT shipments like this one have the proper paperwork associated with them; because for this package there was no notification made that there was HAZMAT to my knowledge. If there is not any paperwork required employees need to be made aware of the types of packages that do not require any paperwork so that they know what does or does not need paperwork associated with it.
Air taxi Captain reported USPS Hazmat package with Lithium Ion battery sticker transported without required documents provided to flight crew.