WCAG Guideline 3.3.4: Error Prevention (Legal, Financial, Data) Explained

Estimated read time: 6–7 minutes

Guideline 3: Understandable

The Understandable principle ensures that users can easily interact with and understand web content, especially when entering critical information.

Guideline 3.3: Input Assistance

Guideline 3.3 focuses on helping users avoid and correct mistakes when entering information, especially in high-stakes situations.

What Is Guideline 3.3.4 Error Prevention (Legal, Financial, Data)?

"For web pages that require the user to submit legal commitments or financial transactions, or modify or delete user-controllable data, at least one of the following is true: submissions are reversible, data is checked for input errors and the user is provided an opportunity to correct them, or a mechanism is available for reviewing, confirming, and correcting information before finalizing the submission."

Guideline 3.3.4 requires extra safeguards for forms and processes involving legal, financial, or critical data.

Helps users avoid costly or irreversible mistakes
Essential for legal agreements, purchases, and data management
Applies to all legal, financial, and data modification forms

For more, see AccessGuide: Legal, Financial, and Data Errors .

Why Does It Matter?

All Users: Need protection from accidental or costly errors
Screen Reader Users: Benefit from clear review and confirmation steps
Accessibility: Reduces risk and increases user confidence

For more, see W3C’s guidance on Error Prevention (Legal, Financial, Data) .

What Needs Error Prevention?

Legal agreements (contracts, terms acceptance)
Financial transactions (purchases, payments)
Data modification or deletion (user profiles, records)

How to Meet Guideline 3.3.4

Make submissions reversible (e.g., undo, cancel)
Check for input errors and allow corrections before final submission
Provide a review and confirmation step before finalizing
Test all critical forms for error prevention safeguards

For more, see the W3C's Error Prevention Techniques .

Common Mistakes to Avoid

Submitting legal or financial forms without a review or confirmation step
Not allowing users to correct errors before finalizing
Failing to provide a way to reverse or cancel submissions

Differences Between A, AA, and AAA for Guideline 3.3.4 in WCAG 2.2

Level AA: Requires error prevention for legal, financial, and data modification forms.
Level AAA: No additional requirements for 3.3.4.
Level A: Not applicable (3.3.4 is a Level AA requirement).

For more, see the W3C’s official documentation for 3.3.4 Error Prevention (Legal, Financial, Data) .

Quick Checklist

Submissions are reversible or can be canceled
Input errors are checked and can be corrected
Review and confirmation step is provided
Tested with screen readers and accessibility tools

Guideline 3.3.4 ensures that users are protected from costly or irreversible mistakes in legal, financial, or data-related forms. Safeguards and review steps are essential for accessibility and trust.

Protection and review are key—make your critical forms safe and accessible for everyone!

AccessiTech LLC