An electronics counter is a few expensive things, not a hundred cheap ones. The argument later is never "did we sell a charger". It is which charger, which serial, and whether the bill the customer is holding is a bill a warranty desk will accept.
What the bill has to carry
The product, the serial or IMEI in the line or the note, the price, and a number you can find again. A screenshot of a wallet payment is not that bill. If the shop is VAT registered, the VAT has to be on it. Electronics is one of the trades that IRD lists, in various years, as compulsory VAT from the first sale rather than from the fifty-lakh line. That list changes. Before you open, ask whether your trade is on the current circular. Do not take this paragraph as the circular.
If you are not on that list and you are under NPR 50,00,000 of goods turnover in the past twelve months, you may still be a PAN bill shop. The distinction is PAN bill vs VAT bill. Adding 13 percent without a VAT registration does not make the warranty stronger.
The counter
A tablet is enough. A desktop is traditional in this trade and unnecessary unless you already live in one for repairs. Stock is one unit per serial, not a pile of identical boxes with a single count, once the thing is expensive enough that a missing piece matters. The hardware money is the same published range as the cafe counter. The clothing version of this page, and the others, start at a clothing shop.