The QPP portal for submission of RY 2021 data appears to be requiring the APP identifier for ACO participants that are only logging in to submit PI data. However, per the QPP website:

"Reminder: If your APM Entity is reporting your quality and improvement activities data, you will still need to submit your Promoting Interoperability data at the individual or group level for traditional MIPS."

Which would seem to imply organizations in this bucket should still submit PI via QRDA III using the MIPS individual or MIPS group identifier.

Can you clarify whether entities that are solely submitting PI data should be using the APP identifier if they're submitting as part of an ACO?