In our post on WCAG 3.3.1 Error Identification, we discussed why it's important to identify and describe user input errors when they are automatically detected. Though that practice is helpful for many users, some may still find it difficult to ascertain the precise nature of an error and correct it; for instance, those experiencing cognitive limitations or people with low or no vision.
For this reason, WCAG 3.3.3 goes a step further and asks that when an input error is automatically detected, possible correction options are provided to users, unless doing so would jeopardize the purpose or security of the content.
These suggestions can take the form of text prompts. Say for instance you are asked to write in the month of your birth, and you enter "5", which is judged to be an incorrect value. The site could reload the form, indicating the error along with a message reading something like "Please provide the name of the month," or "Did you mean 'May'?" In addition to an explicit suggestion, the site could also include further guidance on how to properly fill in and submit the form.