To migrate Account Credits from a previous CRM software you can create a negative product to add to the cart from the POS/Cash Register.
Make sure the product requires a customer and has a GL Code and/or Category that you can track for reporting purposes. Setting the price at -$0.01 allows you to adjust the quantity as needed, using the Qty field in the shopping cart..
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As long as the shopping cart is negative when you check out the 'Apply as account credit' payment type will appear.
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