Best place

Where is the best place to mark your bill, so the other person can find it and track it, on the back where the serial numbers are or on the face part?

I usually put mine on the front in the large blank spot in the upper right. Though, lately I ave been marking in the centre of the front atop of the building image. I can't say what's more effective or not as I've just started doing that.

i usually make certain to NOT compromise any of the security features. i found a stamped note a couple of weeks ago that had the stamp across the "ghost" image – not cool. as well, there is a fine line between marking for our purposes and defacing. let your best judgement guide you.