[Checkpoint] 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) Reversible: Submissions are reversible. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission. [Comments] 
No Accessibility Support impact. This is design-specific. Application or document authors need to consider this provision and ensure conformance. In such forms, PDF authors are able to utilize validation or server-side error-checking prior to final submission.