Following along in MyCase is recommended as you read the article.
Overview
The best way to bring any open invoice balances from a previous software system into your MyCase account would be to create a new invoice for a flat fee totaling that amount. You can then note that it is a balance forwarded from a previous system.
Representing Open Balances from Previous Systems
First, make sure that the fee structure for the case is set up for Flat Fee billing, or a mix of Flat fee and Hourly.
This can be done in the Time & Billing tab of the case.
After you have confirmed the case billing structure, click the Invoices sub-tab on the case page under Time & Billing.
Click Create Invoice.
Make sure to remove any line items that might automatically populate in the invoice as uninvoiced items by clicking the X to the left of the line item (if applicable).
You can invoice these later, after you have represented the open balance from another system.
Find the Flat Fee line and click Add Flat Fee.
Enter the amount of money equal to the open balance from the other system.
Finalize any other necessary categories of the invoice before clicking Save Invoice.
After these steps have been followed, the client will now have an open balance equal to the open balance from the other system.