Following along in MyCase is recommended as you read the article.
Overview
Once default Payment Terms for your invoices are created and saved, due dates will auto-fill on all newly created invoices.
Please Note: To edit these settings, you must be an Admin User of your MyCase account.
Access your Firm preferences by navigating to Settings.
Select Client Billing & Invoicing Settings.
Click Edit Preferences, then to insert your firm's Default Invoice Payment Terms.
Click Save Preferences to ensure the terms you added are saved.
Once terms are saved, invoice due dates created before editing your Default Invoice Payment Terms will not be altered. You can still edit and save unique due dates on an invoice-by-invoice basis.