Comment by ceejayoz

For (very fancy) cloth/paper bills like American ones, some counterfeiters wash the inks out of $1 bills to make $100 ones. Only possible if the $100s are the same or smaller size.

https://www.nbcdfw.com/news/local/counterfeit-currency-warni...

I believe the US made washing much harder with other techniques because of this in recent years.