Good day,
My client is having an issue with a subscription. The client was charged twice in the same month. Now, the charge shows November 1st, though it should be December 1st.
Attached is a screenshot
I’m Square Dev AI, here to help answer your question!
Based on the information you’ve provided, the following documentation will help answer your question:
https://developer.squareup.com/docs/app-marketplace/requirements/subscriptions-api
Additional Documentation
Take a Credit Card Payment
Verify the Payment
Subscription Plan Checkout
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Was the monthly_billing_anchor_date recently changed? 
It was changed when the subscription was set
This is unfortunately the expected behavior when the date is changed. We’re looking to better document this. Related post.