Can group automation move affiliates to a lower group, or work month by month?

No. Group automation with Flows, a Premium feature, only moves affiliates up, and it counts lifetime totals. It doesn't look at a single month, and it never moves an affiliate to a lower group, even when the affiliate's results drop. A flow tracks sales, confirmed referrals or first-time customers, and it moves an affiliate to a higher group when the total reaches the threshold of that group.

A rule that changes each month

A rule such as a higher rate after a month above a sales target, and the standard rate after a month below it, can't run automatically. You can run it by hand with two groups. Starter has one group, so this needs the Basic plan or above.

1. Create one group for each commission rate.
2. Check the sales of each affiliate after the month ends, for example on the Sales tab of Analytics.
3. Open Affiliates.
4. Select the affiliates to move.
5. Click Change group.
6. Choose the new group in Group.

   

7. Click Assign.

Referrals after the move use the commission of the new group. Earlier referrals keep the commission that they got when they were created.