structural:scholar_edition, stylistic:tone
Tax advantages

Most retirement plans (the exception being most non qualified plans) offer significant tax advantages. Most commonly the money contributed to the account is not taxed as income to the employee at the time of the contribution. In the case of employer provided plans, however, the employer is able to receive a tax deduction for the amount contributed as if it were regular employee compensation. This is known as pre-tax contributions, and the amounts allowed to be contributed vary significantly among various plan types. The other significant advantage is that the assets in the plan are allowed to grow through investing without the taxpayer being taxed on the annual growth year by year. Once the money is withdrawn it is taxed fully as income for the year of the withdrawal. There are many restrictions on contributions, especially with 401(k) and defined benefit plans. The restrictions are designed to make sure that highly compensated employees do not gain too much tax advantage at the expense of lesser paid employees.