There are only 3 reasons the bottle already exists a message will come up. (1) You or a colleague already have it in your queue or have scanned it already during pre-registering the batch. Hence it can’t be scanned twice. (2) One of the other fields has been typed with an illegal character e.g. typing a decimal in meter reading or fluid hours or typing L for litres in the fluid added box. (3) The barcode of another sample has been mistyped that happens to match this bottle. FAQ https://learnoilanalysis.com/faq/this-bottle-label-already-exists/