Assuming Humana or Aetna plan is a Medicare Advantage/Replacement plan, original Medicare would take effect on the date of the hospice election. Medicare benefits would continue to cover the beneficiary through the end of the month when the beneficiary revokes or is discharged from hospice alive.
For example, Ms. Smith Humana Medicare Advantage and elects hospice 7/5/2021. On 8/15/2021, Ms. Smith revokes hospice care.
Humana Medicare term: 7/4/2021
Original Medicare effective: 7/5/2021 - 8/31/2021
Humana Medicare effective: 9/1/2021
Medicare Benefit Policy Manual Chapter 9
section 20.4 - Election by Managed Care Enrollees
https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/downloads/bp102c09.pdf
For professional services (CMS-1500 claim forms)
If you are billing for services not related to the treatment of the terminal condition, you will need to bill modifier GW.
Medicare Claims Processing Manual Chapter 11
Section 50 - Billing and Payment for Services Unrelated to Terminal Illness
https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/Downloads/clm104c11.pdf