Is it legal to mark or write on paper currency?

It's ok in the UK. You can even draw glasses on the queen - but it may just be me that does that :-)

How can it be illegal in the USA? The USA has no currency. Federal Reserve notes are not owned by the government of the USA. The Federal Reserve is a private corporation using government printing equipment to produce currency..fiat currency; of which they loan to the government of the USA at interest!

Laws vary world wide ... in some countries there are no laws against it, in other countries it is a very serious treasonous crime against their nation ... in most places it is a minor offense, so although you are not supposed to, the crime is not checked & enforced, so you could easily get away with it ...

... here in Canada it used to be very illegal, but the law was changed back in the late 70s ... before, you could be sent to prison for defacing the image of the queen ... now, lots of jewelry makers carefully cut the maple leaf on the back of a penny, gold plate it, and make & sell ear rings etc., ... and lots of joke stores will make a custom bill for you by printing your photo over the person's picture on any paper money bill you choose ...

It is a crime because you cannot deface paper currency.
That is if you get caught.

i think its a federal crime.

I always write in the margins. I go the www.wheresgeorge.com and register my money. It's a pretty fun site. I don't have a big percentage of hits though.

I was always told it was illegal, but it seems there is always a message on one of my bills. +5

There is nothing illegal about writing or marking on a currency note.
But to keep the bank notes appearing fresh and to make them last long it is advisable not to write anything on the currency notes.

It's only illegal if it deems the currency unusable, drawing a mustache is fine, scribbling in sharpie is not.

its illegal but who cares?