I'm trying to get a better handle on the user experience for a customer with an active introductory offer who upgrades to a subscription with a promotional offer. To give a contrived example: We have two annual subscription products "Regular" and "Plus" in the same subscription group. Plus is an upgrade of Regular. We offer a free trial (introductory offer) with Regular, and want to try to upsell a user to Plus (with a promotional offer) while they're still in their trial period . The documentation suggests that when the new sub is an upgrade, it triggers an immediate billing event – but in sandbox testing it seems that an existing introductory offer trial doesn't get truncated. My understanding is – if the "plus" sub offers a discounted first year via PO, the timeline would be: User acquires initial Regular subscription with free trial User acquires a Pro subscription with a discounted first year during the trial The trial isn't truncated. The user is billed the discounted "Pro" rate for their first year at the termination of the trial. If the promotional offer includes a free trial it's less clear, but I think: User acquires initial Regular subscription with free trial User acquires a Pro subscription with a second free trial The trials run back-to-back, and the user is billed at the "Pro" rate after the second trial. Is this correct? I feel like this must be documented somewhere, but I haven't found where yet.