3.3.4 Error Prevention (Legal, Financial, Data)

What does it mean?

This applies to pages where users make a legal commitment or a financial transaction, change or delete their stored data, or submit test answers. For these, at least one safeguard is needed: the action can be undone, the input is checked and the user can correct mistakes, or the user can review and confirm everything before sending.

A typical solution in a shop is a summary page before "Buy now" where the user can see and change the order. For deleting an account, a confirmation step or a period in which the deletion can be undone works.

Who does it help?

• People with motor disabilities who may click or type something by accident
• People with cognitive disabilities or reading difficulties
• Screen reader users, who may miss a detail in a long form

Common failures

• An order is placed with one click and no summary or way to cancel
• An account or saved data is deleted immediately without confirmation
• A booking form sends wrong dates without showing a review step first

How we test it

• evidence Evidence: our scanner collects material such as screenshots, lists and measurements.

Test question: Orders, contracts and data changes can be reviewed, corrected or reversed before final submission.

A person decides every criterion. No criterion ever passes automatically.

How to fix it

<button type="submit" form="cart">Buy</button>
<!-- order is placed immediately -->

<h2>Check your order</h2>
<dl>
  <dt>Items</dt><dd>2 × Product A</dd>
  <dt>Delivery address</dt><dd>… <a href="/checkout/address">Change</a></dd>
</dl>
<button type="submit">Order with obligation to pay</button>

A review step lets users check and correct everything before the binding order.

Practical tips

• A confirmation e-mail after the purchase does not replace a review step before it.

Guides and patterns on this

• Forms that everyone can completeForms are where people buy, book or give up. This guide shows how labels, required fields and error messages need to work for keyboard, screen reader and magnifier users.

Official source

Understanding WCAG 2.2 at the W3C: 3.3.4 Error Prevention (Legal, Financial, Data)