If a form field is filled in incorrectly, provide suggestions for improvement if possible

If an error has been found and suggestions for improvement are known, these suggestions must be communicated to the visitor. The suggestions can be used to better understand what exactly needs to be filled in.

For many input fields it is known in which format they must be filled in. For example, in the Netherlands, a telephone number consists of 10 digits and a postal code consists of 4 digits and 2 letters. A good error message consists of the statement that the ‘phone number’ field has not been filled in correctly, and that a phone number consists of 10 digits.

Do not write:

  • This field is not filled in correctly..

But write:

  • ‘Date of birth’ is not entered correctly. Use the dd-mm-yyyy format.
  • The field ‘Phone number’ is not filled in correctly. A phone number consists of 10 digits.

A few examples:

  • Date is written in dd-mm-yyyy format.
  • IBAN starts with 2 letters, 2 numbers, 4 letters.
  • Postal code consists of 4 digits and 2 letters.
  • Phone number consists of 10 digits.
  • URL starts with http:// or https://.