You can watch this video to learn how to accept an advance payment. If you’d rather read about it, just scroll down.
This is how you use an Advance to settle an invoice: In the Billings tab, click on the Payments option and click on Add Payments.
If you haven’t already selected a patient, you will see a contacts screen. You can select the patient from here and you will be taken to the next screen
From the right, click on the Invoice that needs to be paid. 
You are now on the payments page. You can see that the Advance amount is automatically entered into the Pay from Advance field.
The amount shown in the Pay Now field is the balance amount that the patient needs to pay. This is calculated by deducting the Advance amount from the total cost of the procedure. Once you’ve entered all the relevant details, click on Save Payment.
After you click on Save Payment, you can see the payment in the Payments page. You can also print out the receipt by clicking on
the Print option in the drop-down box.