Answer by A Quora admin:
The processes are known. The equipment is expensive, the materials are strictly regulated, and the work is extremely difficult. In most cases, especially now.
The Jamaican government went on a crash currency replacement program about 20 years ago because color laser photocopiers made counterfeiting their money a matter of buying $70,000 worth of equipment and pushing a button.
If you acquire the equipment, and manage to make some decent plates, there is a way (at least in the US) to counterfeit a lot of money while having a decent chance of getting away with it – only print ones and fives. No one looks at them twice. No one runs magnetic markers across them to make sure they're real. You can spend them at will for a few days to a few weeks.
But there are problems. Unless you can get ahold of the right magnetic ink (very hard to do), the bills will be detected as soon as they hit a bank. Modern counting machines rely on the magnetism of money, and every bill in a bank is going to be run through a counting machine at some point. Ones and fives will probably get put through while the person depositing them is standing there, so your bogus bills will be detected the next day. Plus you're now dealing with people who handle thousands of bills a day, so it better feel right. You'll have to move around a lot.
And you can't buy anything big – imagine trying to buy a car with ones and fives. And you can't deposit the money. You can't use it in a vending machine, or at a casino.
The biggest obstacle to counterfeiting money is spending it is just as hard as making it.