3.3.4 Error Prevention (Legal, Financial, Data)

For Web pages that cause legal commitments or financial transactions for the user to occur, that modify or delete user-controllable data in data storage systems, or that submit user test responses, at least one of the following is true: (Level AA)

  1. Reversible: Submissions are reversible.
  2. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.
  3. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.


The intention of the success criteria is to prevent people with disabilities making mistakes while dealing with financial transactions, legal commitments and mass data. If a wrong date is selected while booking a non-refundable flight or entered different numbers while purchasing stocks will result in huge financial loss and cannot be recovered. Checking a checkbox for a legal document while purchasing software or any other product by mistake and no mechanism is in place to confirm the commitment. Deleting a record from a data base such as users past transactions which cannot be retrieved are few examples.

Providing the ability to reverse actions allows users to correct a mistake that could result in serious consequences. Providing the ability to review and correct information gives the user an opportunity to detect a mistake before taking an action that has serious consequences.

WCAG 2.0 success criteria 3.3.4 expects content authors to provide any one or more of the following mechanisms to avoid such loss of financial burden, avoid risk of legal commitments or loss of data that is stored on the data base which cannot be retrieved if it is deleted.

  • Reversible: Allow the user to reverse the submission so that they can escape from the risk or loss that happens due to user interaction.
  • Checked: Allow the user to verify the data entered to identify input errors that might be filled in. If the input errors are identified provide a mechanism for the user to correct the mistakes before submission.
  • Confirmed: Provide the user a mechanism to review, confirm and correct the information before finalizing the submission.

Who benefits

  • People with reading disabilities may transpose numbers and letters.
  • People with motor disabilities may hit keys by mistake.
  • People with all other disabilities may be more likely to make mistakes.

WCAG 2.0 Techniques

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