Follow these simple steps:

Step 1 Accrue charges on your account in a spurious fashion e.g. attempt to renew books over the Christmas holidays via phone but receive ambiguous messages
Step 2 Realize you’ve received fines
Step 3 Refuse to pay them
Step 4 Wait 5 years
Step 5 Try to take a book out but the machine won’t let you
Step 6 Librarian gets confused why there’s such old fines on your account and deletes them for you

Et voilà. True story. I kid you not.