How can a reseller partner decrease or increase the amount of licenses for an existing Evergreen (SaaS) subscription?

It is possible to decrease or increase the amount of licenses for an existing SaaS subscription in Partner Portal by following the steps below.

New Partner Portal:

Open the Sales tab from the main menu and go to Accounts
Select the correct customer account from the list
Go to the Deal Ordering & Subscriptions tab and click Amend Contracts
Select Amend Subscriptions and click Next
Set the Amendment Start Date (by default today. Can be set up to 31 days in future)
Select Contract for the amendment and click Next
Verify that you are opening the correct contract by clicking Amend (Quote will open)
Click Amend Products to proceed with quantity change
Select the Amend option to change quantities of subscriptions (you can increase of decrease)
1. If you are reducing the quantity of licenses, the updated monthly contract value will take effect on the 1st day of the next month
2. If contract value remains the same or increases after the amendment, the change will take effect immediately and if done mid-month, proration is applied on pricing
Update the new intended quantity for the subscription on the Quantity field and click Quick Save to view the changes
Click Save to save the quote
Click Generate Order to make the order

Old Partner Portal:

Click the Ordering-tab from the main menu, then click Saas from the sub-menu
Click New SaaS Order
For an existing customer, start typing the customer name into Search or add customer-field and the customer should appear in the suggestions drop-down list -> select customer
Fill in order reference number (partner can choose this themselves, it is an internal reference for the partner helping them identify the customer and transaction and is visible on the bill we send)
Click Add products
Choose sales type as SaaS change (license increase or decrease)
Select subscription to be modified
Fill in new total quantity for the subscription
Click Continue
Click Order to submit the order