You may want to include validation on required fields. This will ensure that when user are interacting with the form they are providing the correct information and also this will cut down on invalid submissions.
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Screen readers will announce "Error" and then any instructions you include in the Error Msg. Upon encounter the field a screen reader will announce "Invalid" and then the contents of the field.
See also Error Action
Additional Documentation by Frevvo
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The following examples were found on frevvo's documetation site linked at the top of this page.
US Zip Code Pattern
A pattern that restricts a text control to only allow strings formatted as a US zip code: ##### or #####-####:
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