What do you do when a dog has eaten your money ? Well, you wait until it comes out, then you soak it, wash it, rinse it, and repeat a lot. Ewww…
But what if it’s been damaged or mutilated to the point where you can no longer use it? That’s when you call in the Bureau of Engraving and Printing  to get a replacement.
If you have more than 50% of the bill, just mail it “Registered Mail, Return Receipt Requested” (or personally deliver it) to the Bureau of Engraving and Printing along with a letter explaining the estimated value of the bill and how it got that way. If you have less than 50%, do the same but you better do a much better job with the letter as they have to believe that the rest of the bill has been destroyed.
If the damaged money are bills, send it to:
Department of the Treasury
Bureau of Engraving and Printing
Office of Currency Standards
P. O. Box 37048
Washington, D. C. 20013
If they are coins, send it to:
U. S. Mint
Post Office Box 400
Philadelphia, PA. 19105
If they aren’t damaged or mutilated and they’re just dirty, defaced, worn out, or a little torn, then bring them back to your bank for a replacement. This only applies if you can definitely tell what the value of it is and it’s clearly more than 50%, though the site doesn’t really tell you what “clearly more” really is. If it’s a little corner tear, that’s probably clearly more.