Printers
The app prints on the receipt printer already paired with Shopify POS. It never connects to the printer itself: POS receives each receipt and sends it to the printer, the same way it prints Shopify's own receipts. Star and Epson receipt printers supported by Shopify POS work.
Pair a printer
In Shopify POS go to Settings › Hardware and connect your receipt printer. Then open Split gift receipts and pick the printer at the bottom of the screen. Receipts are laid out for 80 mm paper and stay readable on 58 mm.
Without a receipt printer
If no receipt printer is connected, the screen says "No receipt printer connected. Pair one in Settings › Hardware, or use the system print dialog." Tap Print via system dialog to print on any printer your device can reach, such as an AirPrint printer on iPhone or iPad.
The printer disappeared
If the printer is switched off or loses its connection, POS says "The selected printer is not connected. Check it and tap Refresh printers." Check the printer, tap Refresh printers, and print again.
If only some receipts printed, POS shows how many, for example "Printed 1 of 2", with the error. Fix the printer and print again; you can remove the receipts that already printed first.