A State's liability for contributions equals the sum of the taxes which would be imposed by sections 3101 and 3111 of the Internal Revenue Code of 1954, if the services of the employees covered by the State's agreement were employment as defined in section 3121 of the Code. The State's liability begins when those covered services are performed, for which wages are actually or constructively paid to those individuals, including wages paid in a form other than cash (see § 404.1041(d)). If an agreement is effective retroactively, the State's liability for contributions on wages paid during the retroactive period begins with the date of execution of the agreement or applicable modification. Where coverage of a coverage group has been terminated, the State is liable for contributions on wages paid for covered services even if the wages are paid after the effective date of termination of coverage.