This info is taken from: https://www.isda.org/countdown-to-phase-6-initial-margin/

As of September 1, 2022, regulatory initial margin (IM) requirements will apply for the first time to hundreds of global counterparties that belong to a consolidated group for which the average aggregate notional amount (AANA) of derivatives transactions exceeds €8 billion, or a similar amount in local currency. This compliance date is commonly referred to as ‘Phase 6’, since it is the sixth global compliance date for the phase-in of regulatory IM requirements since September 1, 2016.

ISDA estimates that more than 775 counterparties with an excess of 5,400 relationships may become subject to regulatory IM requirements in Phase 6. More than 800 of those relationships may need to exchange IM in the near-term following September 1, and therefore should be actively preparing at this stage.

Preparation for regulatory IM is complex and resource intense, involving the bilateral negotiation of new IM documents, the establishment of custodial accounts, and operational preparation for collateral management processing – including margin calculation, margin call communication, allocation, and affirmation, collateral settlement and reporting. It is imperative that a group of counterparties that anticipates it will exceed the AANA threshold for Phase 6 and is likely to exceed the IM threshold of €50 million (or similar in local currency) notifies its counterparties and begins preparation.

ISDA provides and supports documentation and mutualized solutions to help parties prepare for Phase 6.