Update ssn page to include guidance on displaying prefilled last four of ssn

src/_patterns/ask-users-for/social-security-number.md

@@ -5,6 +5,7 @@ sub-section: ask-users-for
 title: Social security or VA file number
 intro-text: "Follow this pattern whenever you need to collect a person's Social Security or VA file number for an application."
 code-link: https://github.com/department-of-veterans-affairs/vets-website/blob/main/src/platform/forms-system/src/js/web-component-patterns/ssnPattern.jsx
+code-link-mask-string: https://github.com/department-of-veterans-affairs/vets-website/blob/main/src/platform/forms-system/src/js/utilities/ui/mask-string.jsx
 example-link: https://staging.va.gov/mock-form-patterns/identification-information
 figma-link: https://www.figma.com/file/4A3O3mVx4xDAKfHE7fPF1U/VADS-Templates%2C-Patterns%2C-and-Forms?type=design&node-id=2988%3A23560&mode=design&t=93yXuwTXsWwWopry-1
 github-title: pattern-ssn
@@ -22,16 +23,22 @@ anchors:
 
 ### When to use this pattern
 
-* **When you need to collect a person's Social Security or VA file number.** For example, for an application for identity purposes.
+* **When you need to collect or display a person's Social Security or VA file number.** For example, for an application for identity purposes.
 
 ## Examples
 
+### Collect
+
 {% include component-example.html alt="Shows the form fields used to obtain Social Security number and VA file number." file="/images/patterns/ask-users-for/social-security-number/form-ssn.png" caption="Example of asking for a Social security or VA file number." class="x2" %}
 
 <a class="vads-c-action-link--blue" href="{{ page.example-link }}">
   View an example
 </a>
 
+### Display
+
+{% include component-example.html alt="Example of a prefilled Social Security number with a label that reads Last four digits of Social Security number' followed by the numbers 6784." file="/images/patterns/ask-users-for/social-security-number/card-ssn.png" caption="Example of a prefilled Social Security number." class="x2" %}
+
 ## How to design and build
 
 ### How this pattern works
@@ -42,28 +49,48 @@ A VA file number is how a Veteran’s claim is tracked through the compensation
 
 * **Use the [web-component-patterns/ssnPattern in the Forms Library]( {{ page.code-link }}).**
 
-The ssnPattern implements the following:
+The ssnPattern implements the following best practices:
 
-* **Use a single text input for each field.**
+* **Prefill Social Security number when possible.** Don't ask users to input their SSN if you can prefill it instead.
+* **Use a single text input for each field.** Don't split the SSN into 3 text inputs.
 * **Do not abbreviate.** Use ‘Social Security number’. Do not use abbreviations, such as SSN.
 * **When asking for both Social Security and VA file numbers, one or the other may be provided.** VA file numbers are not on every form.If the form asks for a Social Security number and VA file number make sure to note in the VA file number label or helper text, "must have this or a Social Security number".
-* **Give user flexibility in entering their Social Security number.** A user can enter the Social Security number however they like: with spaces, without spaces, dashes, or without dashes. When the user enters their number and the input loses focus, the number will appear masked with dashes. 
+* **Give user flexibility in entering their Social Security number.** A user can enter the Social Security number however they like: with spaces, without spaces, dashes, or without dashes. When the user enters their number and the input loses focus, the number will appear masked with dashes.
 * **Validate Social Security numbers.** See [content considerations](#content-considerations) for the appropriate validation messages.
 
 ### Components used in this pattern
 
 * [Text input]({{ site.baseurl }}/components/form/text-input)
+* [Card]({{ site.baseurl }}/components/card)
 
 ### Page templates available for this pattern
 
 Use the [VADS templates (Patterns & Forms) for Social Security or VA file number in Figma]({{ page.figma-link }}).
 
+### Related patterns to this pattern
+
+* [Help users to... Know when their information is prefilled]({{ site.baseurl }}/patterns/help-users-to/know-when-their-information-is-prefilled)
+* [Help users to... Update prefilled information]({{ site.baseurl }}/patterns/help-users-to/update-prefilled-information)
+
 ## Code usage
 
-[ssnPattern is a web-component pattern available in the Forms library]({{ page.code-link }}).
+[ssnPattern is a web component driven pattern available in the Forms library]({{ page.code-link }}).
+
+[formatNumberForScreenReader is a utility function available in the Forms library]({{ page.code-link-mask-string }}). This utility function can be used to format a number for screen readers, such as a Social Security number when it is prefilled.
+
+Example:
+
+```jsx
+const formattedNumber = formatNumberForScreenReader(123456789);
+const ssnPrefillText = () => (
+  <p>
+    Last 4 digits of Social Security number: {formattedNumber}
+  </p>
+)
+```
 
 ## Content considerations
 
 ### Labels, error messages, and hint text
 
-{% include _field-labels.html labels=site.data.content.patterns.ask-users-for.social-security-and-va-file-number %}
+{% include _field-labels.html labels=site.data.content.patterns.ask-users-for.social-security-and-va-file-number %}