# Understanding Error Prevention (Legal, Financial, Data)

## In brief

Goal
  Users can avoid submitting incorrect important information.
What to do
  Provide ways for users to confirm, correct, or reverse important submissions.
Why it's important
  People with disabilities may be more likely to make mistakes, or not notice them.

## Intent of Error Prevention (Legal, Financial, Data)

The intent of this Success Criterion is to help users with disabilities avoid serious consequences as the result of a mistake when performing an action that cannot be reversed. For example, purchasing non-refundable airline tickets or submitting an order to purchase stock in a brokerage account are financial transactions with serious consequences. If users have made a mistake on the date of air travel, they could end up with a ticket for the wrong day that cannot be exchanged. If users made a mistake on the number of stock shares to be purchased, they could end up purchasing more stock than intended. Both of these types of mistakes involve transactions that take place immediately and cannot be altered afterwards, and can be very costly. Likewise, it may be an unrecoverable error if users unintentionally modify or delete data stored in a database that they later need to access, such as their entire travel profile in a travel services web site. When referring to modification or deletion of 'user controllable' data, the intent is to prevent mass loss of data such as deleting a file or record. It is not the intent to require a confirmation for each save command or the simple creation or editing of documents, records or other data.

Users with disabilities may be more likely to make mistakes. People with reading disabilities may transpose numbers and letters, and those with motor disabilities may hit keys by mistake. 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.

User-controllable data is user-viewable data that the user can change and/or delete through an intentional action. Examples of the user controlling such data would be updating the phone number and address for the user's account, or deleting a record of past invoices from a website. It does not refer such things as internet logs and search engine monitoring data that the user can't view or interact with directly.

## Benefits of Error Prevention (Legal, Financial, Data)

- Providing safeguards to avoid serious consequences resulting from mistakes helps users with all disabilities who may be more likely to make mistakes.

## Examples of Error Prevention (Legal, Financial, Data)

Order confirmation
  A Web retailer offers on-line shopping for customers. When an order is submitted, the order information—including items ordered, quantity of each ordered item, shipping address, and payment method—are displayed so that the user can inspect the order for correctness. The user can either confirm the order or make changes.
Stock sale
  A financial services Web site lets users buy and sell stock online. When a user submits an order to buy or sell stock, the system checks to see whether or not the market is open. If it is after hours, the user is alerted that the transaction will be an after-hours transaction, is told about the risks of trading outside of regular market hours, and given the opportunity to cancel or confirm the order.

## Resources for Error Prevention (Legal, Financial, Data)

## Techniques for Error Prevention (Legal, Financial, Data)

### Sufficient Techniques for Error Prevention (Legal, Financial, Data)

#### Situation A: If an application causes a legal transaction to occur, such as making a purchase or submitting an income tax return:

- Providing a stated period of time after submission of the form when the order can be updated or canceled by the user
- Providing the ability for the user to review and correct answers before submitting
- Providing a checkbox in addition to a submit button

#### Situation B: If an action causes information to be deleted:

- Providing the ability to recover deleted information
- G168: Requesting confirmation to continue with selected action
- Providing a checkbox in addition to a submit button

#### Situation C: If the Web page includes a testing application:

- Providing the ability for the user to review and correct answers before submitting
- G168: Requesting confirmation to continue with selected action

### Additional Techniques (Advisory) for Error Prevention (Legal, Financial, Data)

- Providing client-side validation and alert
- Providing success feedback when data is submitted successfully

### Failures for Error Prevention (Legal, Financial, Data)