govuk-frontend/dist/govuk/components/checkboxes/template-with-single-option-set-aria-describedby-on-input.html

GOV.UK Frontend contains the code you need to start building a user interface for government platforms and services.

<div class="govuk-form-group govuk-form-group--error">
  <p id="t-and-c-error" class="govuk-error-message">
    <span class="govuk-visually-hidden">Error:</span> Please accept the terms and conditions
  </p>
  <div class="govuk-checkboxes" data-module="govuk-checkboxes">
    <div class="govuk-checkboxes__item">
      <input class="govuk-checkboxes__input" id="t-and-c" name="t-and-c" type="checkbox" value="yes" aria-describedby="t-and-c-error">
      <label class="govuk-label govuk-checkboxes__label" for="t-and-c">
        I agree to the terms and conditions
      </label>
    </div>
  </div>
</div>