My customer reported a duplicate charge on the subscription

Our system is designed to prevent any duplicate charges, meaning that it was designed in a way that each renewal will have only one charge tied to it, meaning that having a duplicated charge which would be caused by the system is practically impossible.

But if you suspect that a duplicated charge happened on a specific subscription, then we recommend that you first check the following things:

1.) Check if the customer has more than one subscription in your shop. It happens occasionally that customers have one subscription in a shop and then also start another one a few weeks later (usually due to a misunderstanding). If these subscriptions renew on the same day, the customer might report it as “duplicate charge” while these were actually 2 separate charges, each for it's own subscription.
If this is the case, we recommend that you contact the customer and cancel one of those subscriptions.

2.) Sometimes, it happens that a payment has failed and the customer didn't know that a payment will automatically be retried, so they manually triggered another separate renewal of a subscription. Then, if both payments go through, the customer can see this as “duplicate charge” while in fact it happened because they manually triggered a separate renewal.
If this is the case, we recommend that you explain this to the customer so you avoid this happening in the future and refund one of their orders.

3.) It can also happen that a customer requested an earlier renewal of their subscription, but didn't realize that they already have a renewal scheduled for the next day. The customer can also report this as "duplicate charge". If that happens in your case, we recommend that you also contact the customer, explain this to them and refund one of the orders if needed.

If none of these apply, then you can contact our support and ask for some help to figure out what happened in your case. We will make sure to get to the bottom of it.