To define data as missing, use the cogwheel to select the option 'user missing' and from the provided list, indicate the reason why the data is missing. 

Here are the default values / reasons you can choose from:

• Measurement failed (-95)
• Not applicable (-96)
• Not asked (-97)
• Asked but unknown (-98)
• Not done (-99)

The accompanying numbers (shown in brackets) denote the numerical value that the data will be displayed with in the export. These cannot be changed or customised.

If a 'user missing' value is defined in error or data later becomes available for the field, you can simply click on the cogwheel next to the appropriate data point and uncheck the 'User missing' box to re-enable data entry. The same applies if you have assigned a whole form/visit as user missing, this should be corrected for each field in that form/visit.

Please note - it is not possible to edit the reason once user missing is added to a field. It is possible to select 'user missing' again which clears the value and then you can repeat the procedure to provide the correct reason.