Can't Delete Old Customers

Can't Delete Old Customers

How do we delete canceled customer accounts? Zoho doesn't appear to have an archive feature, and it won't allow us to delete accounts that have transactions in Books. Considering all the accounts have transactions, we're getting a bit of a build-up of completely useless data. We have accounts closed in 2015 that we can't get rid of.
Is there a solution or are we supposed to just fill our CRM with canceled accounts?