Heads fellow members, counterfeiters are passing fake money more often lately to unwary businesses especially during the holidays. There have been already several reports in my area of fake $100 and $50. If you have a 365 nM UV light you can check for the embedded stripe both verifying it location and bill value just in case someone washed a lower bill and reprinted a higher value. Nearly all bills paper will be dark otherwise; although, I seen a hand of ones that are a little brighter but the Feds haven't put any stripes in them.
Here is an example of what you are looking besides to other know counterfeit preventative measures build in the US Federal Reverse Notes.