WHAT HAPPENS WHEN MULTIPLE ENTITIES ARE INVOLVED IN RENDERING CARE? 

When multiple entities are involved in rendering care, it is not necessary to give separate ABNs. Either party involved in the delivery of care can issue the ABN when:
                 
There are separate “ordering” and “rendering” providers (e.g., a physician orders a lab test and an independent laboratory delivers the ordered tests).

One provider delivers the “technical” and the other the “professional” component of the same service (e.g., radiological test that an independent diagnostic testing facility renders and a physician interprets).

The entity that obtains the signature on the ABN is different from the entity that bills for the service (e.g., when one laboratory refers a specimen to another laboratory, which then bills Medicare for the test).

Regardless of who gives the notice, the billing entity will always be held responsible for effective delivery. In these situations, it is permissible to enter the names of more than one entity in the header of the notice.
LACK OF ABN NOTIFICATION
A provider will likely have financial liability for items/services if he knew or should have known that Medicare would not pay and fails to issue an ABN when required or issues a defective ABN. In these cases, the provider cannot collect funds and is required to make prompt refunds if funds were previously collected.
COLLECTION OF FUNDS AND REFUNDS
Collection of Funds
A beneficiary’s agreement to be responsible for payment on an ABN means that the beneficiary agrees to pay for expenses out-of-pocket or through any insurance other than Medicare. The provider may bill and collect funds for non-covered items/services immediately after an ABN is signed. 
If Medicare ultimately denies payment, the provider retains the funds collected. However, if Medicare pays all or part of the claim for items/services previously paid by the beneficiary or if Medicare finds the provider liable, the provider must refund the beneficiary the proper amount in a timely manner. Refunds are considered timely when made within 30 days of the notice of the claim denial from Medicare or within 15 days after a determination on an appeal if an appeal is made.
HOW LONG SHOULD AN ABN BE KEPT ON FILE?
In general, the ABN should be kept for five years from discharge/completion of delivery of care when there are no other applicable requirements under state law. Providers are required to keep a record of the ABN in all cases, including those cases in which the beneficiary declined the care, refused to choose an option or refused to sign the notice.