When using RedSys payment plugin it is imperative that you change the numbering of the Orders by going to the back end > Taxi Booking > Settings > Order email settings Set "Enable Custom Invoice number: Yes" Use these options to construct your order numbering: Y - the current year in 4 digits y - the current year in 2 digits m - the current month in 2 digits d - the current day in 2 digits n - the subsequent number of the invoice for each day Please use "n" as a mandatory option to avoid Order number duplicates which will create problems. Make sure you "Save" the settings after you are done editing.