Sell without internet

The sale is saved on the device first. It uploads when the network comes back.

InvUltra writes the cart, the sale, and the stock change on this device. The screen does not wait for the server.

What to do when Wi-Fi drops

Keep selling. Search, cash, and the receipt still work.
Watch the sync icon. Those sales are queued, not lost.
When the internet returns, leave the app open. The queue sends itself. Stock, invoices, and reports catch up.

A completed sale while the offline banner is visible

Sync icon after the network returns, with the queue clearing

What does not work offline

Opening the register, closing the day, checking a promo code, issuing a purchase return, and applying some credits need the server. The list is What needs internet.

A promo code that cannot be checked must not be forced through. Take the sale without that code, or wait for the network.

Next: Cash in and cash out.