Ship one parcel when a customer orders twice

ShipRules finds unfulfilled orders from the same customer to the same shipping address and merges them into a single order, automatically or after your approval, so you pack and ship once.

Install ShipRules from the Shopify App Store. Already installed? Open it from Apps in your Shopify admin.

• Finds the duplicates for you. Fully paid, unfulfilled orders from the same customer to the same address, placed within a time window you set, are matched up as merge candidates. Approve each one in the merge queue (the default), or switch to automatic merging and run it from Shopify Flow. Tag an order to keep it out.
• Never re-bills the customer. The moved items land on the kept order at no charge, since they were already paid for. The duplicate order is cancelled and its shipping charge refunded. The kept order's total and payment stay as they were.
• Logged, and undoable. Every merge attempt, automatic or approved, successful or failed, is recorded with the orders involved, the outcome and the shipping cost saved. If a merge was wrong, Undo takes the moved items back off the kept order and refunds the cancelled order in full.