Question: I am new to coding for Medicare beneficiaries, and I'm still trying to master all the ins and outs of advance beneficiary notice (ABN) coding. I have two questions: What is the difference between a mandatory and a voluntary ABN? and What role do G modifiers play in ABN coding? Oklahoma Subscriber Answer: Advance beneficiary notices (ABNs) are forms that you'll get the Medicare patient to sign when the payer won't - or might not - pay for all or part of a procedure or service. If you obtain a signed ABN through the proper patient channels, it gives the practice the right to bill the patient for any portion of the procedure or service Medicare might not pay for. Mandatory vs. voluntary: A mandatory ABN is for situations when a provider must issue an ABN, as directed by its Medicare Administrative Contractor (MAC). In those cases, you will consider the signed ABN mandatory in order to go forward with the service. There are other instances where ABNs are voluntary - a provider can issue an ABN as a courtesy, but is not officially required to by Medicare. This example of a voluntary ABN can be given to a patient for an item or service that Medicare never covers ( i.e., fails to meet the definition of a Medicare benefit or service). In these cases, the beneficiary does not need to sign the form or check off any boxes as they would for a mandatory ABN. Mandatory affects modifier choice: Depending on the service and the nature of the ABN, you will want to choose from one (or more) of four modifiers when issuing (or opting not to issue) an ABN: For more information on proper ABN use, see: https://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNProducts/Downloads/ABN_Booklet_ICN006266.pdf.