Our use case involves yearly subscriptions with free products shipped out to members on a monthly basis. Our process was to make a billing cycle edit for the month, add the free item along with free shipping, remove the original product, and commit the changes. We then submit a billing attempt for the $0 billing cycle, which in turn creates the $0 order in shopify.
Starting May 1, the free billing attempts began failing with error code “amount_too_small” and message “Amount must be at least $0.50 usd”. Nothing about our process has changed in months. We have had no issues submitting these $0 billing attempts until now. It seems like something has changed in shopify’s contract billing system that causes it to actually trigger a charge instead of skipping charging the user’s payment method on $0 orders.