Where can I find the status of my contacts?
Click on the contact card and then on the Account Status tab to access the summary of transactions.
How do I create a credit for a customer?
Go to the card of the customer in question, then click on the "Credits" tab. The credit will not be reported to the calendar, but you may use it to settle a transaction.
How to use a credit to settle a customer's bill?
Add a payment to the invoice in question and choose "Credit" as your payment method. The amount will automatically be deducted from the credit available to the customer.