7.5. Add required or aria-required="true" to mandatory fields
Required fields must have a required or aria-required="true" attribute.
Note
In addition to this attribute, a distinctive sign must be included in the <label> tag.
<label for="email">Your email *</label> <input type="email" id="email" name="email" autocomplete="email" required />
<input type="checkbox" id="conditions" aria-required="true" /> <label for="conditions">I accept the conditions of sale (required)</label>