Pairing a printer, once
A Bluetooth printer pairs with the phone the way any Bluetooth device does and is then selected once in the app settings. A USB printer connects to the computer and prints from the browser. Standard ESC/POS printers sold in India work without configuration. The two problems that come up are a printer set to the wrong roll width in its own hardware settings and paper loaded the wrong way round, both of which take a minute to sort out on the setup call.
Choosing 80mm or 58mm
The 80mm roll fits a readable item description alongside quantity, rate and amount in proper columns, and is the right choice for any shop whose bills run past a few lines. The 58mm is narrower and cheaper on consumables, but long material names wrap onto a second line and a fifteen-line bill becomes hard to read. For a hardware or general store, the small extra cost of 80mm is worth it.
What goes on the roll
Your shop name, address, phone number and GSTIN print at the top and a UPI QR can print at the bottom, so the customer pays from the receipt in their hand rather than asking for your number. Keep everything else short — a roll is not the place for terms and conditions. Where a buyer needs the full document, share the A4 PDF on WhatsApp from the same bill.
Printing when the connection is down
Thermal printing over Bluetooth works alongside offline billing on the app, so a power cut that takes out your internet does not stop the counter. The bill is recorded on the phone, printed for the customer, and synced when coverage returns. Nothing about the receipt the customer receives is different.
What a roll costs to run
Thermal paper is the only consumable — there is no ink, no toner and no cartridge. An 80mm roll runs a few hundred bills and costs a small amount, so the running cost of a counter is measured in tens of rupees a month rather than thousands. Buy decent paper: cheap thermal rolls fade within months, which matters when a customer brings a receipt back for a warranty claim or a return. For anything that has to survive years, the A4 PDF is the copy that counts, and it is stored in the account whether or not the paper survives.