401(k)是美国的一种退休储蓄计划，以内部税收法典的一个章节命名。它是许多雇主提供的一种税收优惠退休账户，旨在帮助员工为退休储蓄。以下是401(k)计划的工作原理解释：

1. 员工贡献：在401(k)计划中，符合条件的员工可以选择将他们的税前工资的一部分自动从工资中扣除，并存入他们的401(k)账户。这些贡献通常受到美国国内税务局（IRS）规定的年度限额的限制。
2. 雇主贡献（可选）：一些雇主可能选择匹配员工贡献的一部分作为福利。例如，雇主可以提供匹配员工贡献的50%，最高不超过员工工资的一定百分比。
3. 税收优惠：401(k)计划中的贡献是税延的，这意味着它们在缴纳时不受联邦所得税的影响。这使得您的投资可以在退休时免税增长。
4. 投资选择：401(k)计划通常提供一系列投资选择，如共同基金、股票、债券，有时甚至包括根据您预期的退休日期自动调整投资的目标日期基金。
5. 分期归属：雇主的贡献，包括匹配贡献，可能受到分期归属计划的限制。分期归属确定了您何时完全拥有雇主贡献的资金。随着时间的推移，您将完全拥有资金，这意味着如果您离开公司，可以携带所有雇主贡献的资金。
6. 贡献限额：IRS为401(k)计划设定了年度贡献限额。这些限额可能会年年变化，也可能会根据您的年龄等因素而有所不同。截至2021年9月的更新，员工贡献的年度限额为19,500美元，50岁及以上的人可以额外贡献6,500美元。
7. 提取：您可以在达到59岁半后开始无需支付罚金的情况下从401(k)中提取资金。但是，如果在此年龄之前提取资金，可能会产生10%的早期提取罚金，以及正常的所得税。有一些例外情况，例如某些医疗费用或首次购房，您可能能够避免罚金。
8. 强制最低提取额（RMDs）：一旦您达到72岁（或者如果您在1949年7月1日之前出生，则为70岁半），您必须开始从您的401(k)账户中提取强制最低提取额（RMDs）。这些提款是强制性的，并且应纳税。
9. 可携带性：如果您换工作，通常可以将您的401(k)资金滚动到新雇主的计划中，或者滚动到个人退休账户（IRA）中，以避免早期提款罚金，并保持退休储蓄的税收优惠状态。

值得注意的是，401(k)计划旨在成为长期的退休储蓄工具，如果可能的话，应避免提前提款，以最大化税延增长的好处。此外，401(k)计划受到法规和规定的约束，可能会随时间而变化，因此了解您计划的具体细节并在有关退休储蓄策略方面咨询财务顾问是至关重要的。

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A 401(k) is a type of retirement savings plan in the United States that is named after a section of the Internal Revenue Code. It is a tax-advantaged retirement account offered by many employers to help their employees save for retirement. Here’s an explanation of how 401(k) plans work:

1. Employee Contributions: In a 401(k) plan, eligible employees can choose to have a portion of their pre-tax salary or wages automatically deducted from their paychecks and deposited into their 401(k) account. These contributions are often subject to annual limits set by the IRS.
2. Employer Contributions (Optional): Some employers may choose to match a portion of their employees’ contributions as a benefit. For example, an employer might offer to match 50% of an employee’s contributions up to a certain percentage of their salary.
3. Tax Advantages: The contributions made to a 401(k) plan are tax-deferred, meaning they are not subject to federal income tax at the time they are contributed. This allows your investments to grow tax-free until you withdraw the money in retirement.
4. Investment Options: 401(k) plans typically offer a range of investment options, such as mutual funds, stocks, bonds, and sometimes even target-date funds, which automatically adjust your investments based on your expected retirement date.
5. Vesting: Employer contributions, including matching contributions, may be subject to a vesting schedule. Vesting determines when you have full ownership of employer-contributed funds. Over time, you become fully vested, which means you can take all employer-contributed funds with you if you leave the company.
6. Contribution Limits: The IRS sets annual contribution limits for 401(k) plans. These limits can change from year to year and may vary based on factors like your age. As the update in September 2021, the annual limit for employee contributions was $19,500 for individuals under 50, with a catch-up contribution of an additional $6,500 allowed for those aged 50 and older.
7. Withdrawals: You can start withdrawing funds from your 401(k) without penalties after you reach the age of 59½. However, if you withdraw funds before this age, you may incur a 10% early withdrawal penalty, in addition to regular income tax. There are some exceptions, such as for certain medical expenses or first-time home purchases, where you may be able to avoid the penalty.
8. Required Minimum Distributions (RMDs): Once you reach the age of 72 (or 70½ if you were born before July 1, 1949), you must begin taking required minimum distributions (RMDs) from your 401(k) account. These withdrawals are mandatory and are subject to taxation.
9. Portability: If you change jobs, you can often roll over your 401(k) funds into a new employer’s plan or into an Individual Retirement Account (IRA) to avoid early withdrawal penalties and maintain the tax-advantaged status of your retirement savings.

It’s important to note that 401(k) plans are designed to be long-term retirement savings vehicles, and early withdrawals should be avoided if possible to maximize the benefits of tax-deferred growth. Additionally, 401(k) plans are subject to regulations and rules that may evolve over time, so it’s essential to stay informed about the specific details of your plan and consult with a financial advisor if you have questions about your retirement savings strategy.