Can a duplicate invoice occur?
No, as long as Boekvogel is the only integration booking in this administration. Shopify sometimes sends the same notification twice, for example after a disruption. Boekvogel recognises that and books each order once. Switching from another integration? Read switching.
How that works
Every notification from Shopify gets its own identifier, which Boekvogel stores. If the same notification comes in again, it is recognised and ignored. On top of that, Boekvogel remembers per order which document was created in Moneybird; if it already exists, no second one is made.
See two anyway?
Then the second one almost certainly did not come from Boekvogel: for example an invoice you had created manually earlier yourself, or an import from another system. Email us the order number and we will look at the log with you.