The option to delete an organization is not available on the interface. However, if you can send us a request with a reason for deleting the organization, we might be able to help. But from the past requests received, we've seen that users delete organizations and go over the hassle of setting up a new one for trivial things which could be very easily sorted out. We've listed them below with the solution:
Go to "Settings" → "Organization Profile" to change the organization's name
You should be able to delete any data that you've entered into the account. Check our help section for instructions.
Here again the solution would be to delete all the transactions.
Zoho Invoice FAQ