Can I update the billing date of a subscription by changing the monthly billing anchor date?
Also, does this method only apply to monthly subscriptions, or is there support for other billing timelines like annual billing?
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
https://developer.squareup.com/docs/squarebridge/business-central/payments/collect-payments
Additional Documentation
Onboard to Square Appointments
https://developer.squareup.com/docs/squarebridge/business-central/onboard
Guidelines and Limitations
If this documentation helped you find a solution, please check the box indicating that this reply solves the problem.
Otherwise one of our Developer Advocates will provide additional assistance shortly.
Variations with a MONTHLY cadence (including multiple months, such as QUARTERLY , EVERY_SIX_MONTHS , and ANNUAL ) can be configured to bill on a specific numbered day of the month by setting the monthly_billing_anchor_date when creating or updating a CatalogSubscriptionPlanVariation . For example, a plan variation with a monthly_billing_anchor_date of 15 always bills (by charging the card on file or emailing the customer an invoice) on the 15th day of the relevant month, regardless of the start_date of a specific subscription. 
To confirm, if the retrieveSubscription endpoint doesn’t return a monthly billing anchor date field for annual subscriptions, will updating the monthly billing anchor date still change the billing date for those subscriptions?
Also, why isn’t the anchor date included in requests for annual billing cycles?
Was the subscription created with a monthly_billing_anchor_date? If it wasn’t created with one then it’s expected to not be present.
Ahh, I understand. You need to explicitly set a monthlyAnchorBillingDate when calling createSubscription. Is that correct?
Yep, that is correct.