Offer your thoughts or opinion on the input financial query or topic using your financial background.

What is the lifespan of a series of currency?
US currency doesn't expire, it is always legal tender.  I can see some trouble if you tried to spend a $10,000 bill (you'd be foolish to do so, since they are worth considerably more). Maybe some stores raise eyebrows at old-style $100's (many stores don't take $100 bills at all), but you could swap them for new style at a bank if having trouble with a particular store. Old-series currency can be an issue when trying to exchange US bills in other countries, just because it doesn't expire here, doesn't mean you can't run into issues elsewhere. Other countries have different policies, for example, over the last year the UK phased in a new five pound note, and as of last month (5/5/2017) the old fiver is no longer considered legal tender (can still swap out old fivers at the bank for now at least).  Edit: I mistook which currency you took where, and focused on US currency instead of Canadian, but it looks like it's the same story there.