Connections drop at the worst moment: a full queue and a customer holding cash. The till keeps working, and the work gets sent when the signal returns.
Sell as normal
Cash and recorded mobile money sales are saved on the till with a temporary receipt number. Card and provider payments wait until you are back online, because they need the provider to confirm them.
Nothing is counted twice
Every sale carries its own identifier, so a retry never creates a second sale. When the till reconnects, queued sales are numbered and your stock updates in the order they happened.
