USA: Double taxation agreement, Exchange of Notes: Article 3
With reference to sub-paragraph (o) of paragraph 1 of Article 3 (General Definitions):
it is understood that pension schemes shall include the following and any identical or substantially similar schemes which are established pursuant to legislation introduced after the date of signature of the Convention:
(a) under the law of the United Kingdom, employment-related arrangements (other than a social security scheme) approved as retirement benefit schemes for the purposes of Chapter I of Part XIV of the Income and Corporation Taxes Act 1988, and personal pension schemes approved under Chapter IV of Part XIV of that Act; and
(b) under the law of the United States, qualified plans under section 401(a) of the Internal Revenue Code, individual retirement plans (including individual retirement plans that are part of a simplified employee pension plan that satisfies section 408(k), individual retirement accounts, individual retirement annuities, section 408(p) accounts, and Roth IRAs under section 408A), section 403(a) qualified annuity plans, and section 403(b) plans.