One of my sons found a 20 Pound note and he wanted me to exchange it for him. I went to 2 credit unions and they don't exchange money. I live in Poughkeepsie, NY, so where do I exchange it??
Let's determine potential collectability before exchanging it. In fact, depending on its age the only way you may be able to exchange it is if you sold it to a collector, brought it to exchange at a bank in England, or found someone who lives there or would otherwise be visiting and could exchange it for you. With that said, it would be good to know what condition it is in and what the copyright year is on the note (if it has one). The simplest thing to do is to post clear pictures of both sides of the note and we can go from there.
Agreed with @NOS but it is also worth noting that the £20s in the UK moved from rag paper to polymer some time ago, and I believe that the transition period has ended. If it is just a regular £20, and not collectible or polymer, you will have to go to the Bank of England service counter in London, or have an account / relationship with one of the 'clearing banks' (ie Lloyds, Barkley's etc) to get rid of it. This being said, I own a copy of the Banknote Yearbook, and would gladly look it up if you provide pics.
List it on Craigslist. Exchange it with someone near you who might be willing to purchase it from you. I lived in Beacon NY a few years ago. I would of been someone that could of been interested in it. But don't think you will get a lot in exchange.. I also say you should post pictures of it.