Best practice and help
Use a field description to inform the user how you will use their data:
We place the additional description in a <span> within the <label>:
<label for="email"> Email <span>We will use this to send you the result of your aplication</span> </label>
For reference numbers, provide examples of formatting and where the number may be found:
Alert!Avoid using placeholder text inside form inputs. Placeholder text disappearing when input fields are focused on by the user can be confusing, and may adversely affect how assistive technologies read the content.