Make sure users are entering their data in the correct format with the Enforce Answer Meets Requirements feature.
When creating a custom question in Question Manager you can turn on the Enforce Answer Meets Requirements checkpoint.
The following checkpoints will appear, allowing you to enforce the length and type of data that is allowed to be input into the field.
This is an option for all text field Question Types.
A good example of when you would activate this setting is when capturing bank details for paid staff as it is important for payroll purposes that the format is correct.