Depends who you want to fool. If it's a human-to-human transaction in a busy setting (like a marketplace transaction or something similar) it's pretty easy to s

Depends who you want to fool. If it's a human-to-human transaction in a busy setting (like a marketplace transaction or something similar) it's pretty easy to slip a simple fake without getting caught. Especially if you mix it with real currency and only use small bills. I remember watching a news report a few years ago where the journalist tried doing just that (with photocopied euro bills on regular paper without any clever trick) and he had a pretty high success rate. That being said I can't really imagine anybody doing that at a big enough scale that somebody would bother tracing printer dots back to them. I don't think the authorities are going to bother with that if you slip a dozen fake 10 euro bills around Paris. I guess it can be dissuasive though, keeping honest people honest.