Similar to how you can map a date field in the required format to your XML (e.g. dd/mm/yyyy can be mapped to XML as YYYY-MM-DD), we need a way to map reference numbers correctly to XML. Many back office systems include a check digit on the end of the customers account reference number. So to a customer, we ask for their full reference number (inc check digit) on the form, however the API call only requires the actual account reference number to update the back office system. We need a way to format the refence number entered on the form to the appropriate length in the XML (same as eMapper options for dates). Example. Council tax account reference entered by customer 152006463866 (12 digits inclusive of check digit). I want to map the first 11 digits / trim the last digit so that the actual account number 15200646386 populate the XML payload and update our back office system.