2006: Pension Protection Act (PPA); amends ERISA, requires more rapid funding of under-funded defined benefit plans, facilitates automatic enrolment and investment advice in 401(k) plans and clarifies the legal status of cash balance plans.

2001: Economic Growth and Tax Relief Reconciliation Act (EGTRRA); amends ERISA, increases contribution and benefit limits, improves transferability between different types of defined contribution plans and regulates faster vesting for employer matching contributions to 401(k) plans.

1994: Uruguay Round Agreements Act; amends ERISA, requires greater contributions to under-funded defined benefit plans and limits the range of interest rate and mortality assumptions used to establish funding levels.

1986: Tax Reform Act; amends ERISA, establishes faster minimum vesting rules, limits the effect of integration with the social security scheme, expands coverage of non-highly compensated employees and imposes an excise tax on excess plan assets that revert to an employer upon winding up of a pension plan.

1984: Retirement Equity Act; amends ERISA, requires that when a plan provides pensions at retirement, survivorship pensions must be provided unless the spouse waives the right in writing to survivorship pension.

1978: Revenue Act; establishes 401(k) plans (enabling regulations released in 1981).

1974: Employee Retirement Income Security Act (ERISA); most important complementary occupational pension plan law in the United States. Provides for protection of rights through regulation of participation, vesting, funding, fiduciary standards and reporting, and through the establishment of the Pension Benefit Guaranty Corporation (PBGC), which pays benefits in the case of financial failure of defined benefit plans.

1947: Labor-Management Relations Act (also known as Taft-Hartley Act); provides guidelines for the operation of pension plans administered jointly by employer and employee trustees.

1942: Revenue Act; establishes for the first time the principle that benefits are to be provided to non-highly compensated employees on a non-discriminatory basis.

1928: Revenue Act; allows employers to claim tax deductions for reasonable amounts contributed to pension plans.

1921: Revenue Act; exempts pension trust investment earnings from current taxation.