Archimedes Finance

Become a better investor

Setting up a 401(k)

Lesson in Course: Finance at work (beginner, 8min )

Our job offers a 401(k). How do I set it up?

As we learned in the lesson about retirement accounts through work, 401(k)s help us save for retirement. Since they are only available through our employer, we'll have to enroll in a new 401(k) whenever we switch jobs. 

Unfortunately, the details and enrollment for these plans are often shuffled into the overwhelming stack of onboarding paperwork. It's easy to forget the options we selected or remember if we've provided all the required information.

Here are things to know about our 401(k) plan:

Requirements and eligibility

The U.S. passed the Employee Retirement Income Security Act of 1974, known as ERISA, to standardize retirement plan practices. It spells out the minimum plan requirements and eligibility. While ERISA sets the standard, companies can offer exceptional perks by going above and beyond the minimum requirements.


Usually, we have to be at least 21 years old to participate in a 401(k). We are allowed to contribute until the last day before retirement.


In 2019, 401(k)s became eligible for full-time and long-term part-time employees when the Setting Every Community Up for Retirement Enhancement (SECURE) Act became law.

The requirement for full-time employees is 12 months of service. After which, all employees older than 21 must be allowed to participate in the 401(k) plan.

For part-time employees, anyone who's worked at least 500 hours in the last three consecutive years (and are 21) must be allowed to participate in 401(k) plans.


The IRS limits how much income counts toward calculating our contributions as a percent of our income.

For example, the IRS limits the amount of compensation eligible for 401(k) contributions to $290,000 in 2021. The income limit doesn't exclude anyone who makes more than $290,000 in a given year. Instead, every dollar beyond $290,000 is not eligible for contribution.


Many employers will match our 401(k) contributions, but that doesn't mean that we own that money right away. Sometimes we have to work at the company for a certain period before it's entirely ours. We call this vesting.

A vesting schedule is a timetable to receive the money that an employer added to our 401(k). The vesting schedule is to reward employees who stay at the company. 

Companies often create vesting schedules with a cliff or graded structure. A cliff means we don't own any of our employer's contributions until after a certain period, but we'll own all of it afterward. In a graded vesting schedule, we own parts of the contributions over time.

Vesting examples

The table shows a 3-year cliff vesting schedule and a 6-year graded vesting schedule. 

The 3-year cliff vesting means we don't own any of our employer's additions to our 401(k) until after 3 years. After that period, all of the contributions become ours.

The 6-year graded schedule means we own 20% after 2 years, 40% after 3 years, 60% after 4 years, 80% after 5 years, and 100% after 6 years.

Not all companies require vesting, and some offer employee-friendly schedules. Since vesting applies only to the money contributed by our employer, we always own 100% of our pre-tax contributions.


Plan elections

Whenever we start a new job that provides a 401(k) plan, we need to make several decisions. If we are existing employees, we can reconfirm our choices at any point.

Opt-in or opt-out

The first choice to make is if we want to participate in the 401(k) plan. 

Barring life emergencies, this should always be yes (opt-in). Even if it's only a few dollars per paycheck, every little bit counts towards retirement and lowering our taxes for the year.

pre-tax or post-tax

Some companies offer Traditional and Roth 401(k)s. Contributions to Traditional accounts are pre-tax, while contributions to Roth are post-tax.

If we want to lower how much we pay in taxes today, we would consider a Traditional account. Pre-tax means that we make our contributions from our paycheck before paying income taxes. For example, if we contribute $10,000 to our 401(k) and our salary is $80,000, we would only pay income taxes on $70,000. However, we will need to pay income taxes when we withdraw the money in retirement.

The benefit of choosing a Roth and making post-tax contributions is that we've already paid income taxes, so we won't have to pay any taxes when it's withdrawn in retirement.

Income deferment

Income deferment is how much of our salary or yearly earnings we want to save.

Most 401(k) plans show the amount contributed from our paycheck as a percentage of wages. For reference, 5% is a great starting point for most folks. We can go higher, say 10%, to save more aggressively. Some 401(k) plans allow us to pick a flat dollar amount instead of a percentage.


Beneficiaries are those who receive this money if something happens to us.

Plans automatically assign us as the primary beneficiary, but we can select a contingent beneficiary. If we're married, our spouse defaults as the contingent beneficiary. We can also choose to add any family member, including parents or kids. When adding beneficiaries, we need to provide each beneficiary's social security number and birthdate.

Investment choices

Most 401(k) accounts are very similar to our brokerage accounts, allowing us to pick investment options.

All 401(k)s offer mutual funds, while some 401(k)s offer ETFs. Professional investment managers have made it easy for us to save for retirement by creating target-date funds. These are simple investments that provide investment strategies based on the year we plan to retire. We can learn more about them by checking out the lesson on target-date funds.


Automated elections

Sometimes, there isn't paperwork for us to fill out or make all of these choices upfront. Some employers use an auto-enrollment process, making default selections for us. Auto-enrollment is convenient for employees and increases participation, but we should double-check them to fit our financial circumstances. 

Here are some standard auto-enrollment features that we can change at any time:

  1. Opt-in vs. opt-out — some companies will automatically enroll us into the 401(k) plan, giving us 30 to 90 days to opt-out. They will open a 401(k) account for us if we don't opt-out.
  2. Automatic contribution — our employer might automatically set a 3% salary deferral as our contribution. Companies do this to increase participation rates and lower administrative fees.
  3. Auto-investment — many employers and plan administrators use a default investment for our contributions, like a target-date fund based on our date of birth.

We should review these elections every year and update them to match our needs.

Supplementary materials

Eligibility and participation information can be found on the IRS website:

Actionable ideas

If it's been a while, we should log into our 401(k) account to ensure all of the information is up to date and our deferral rate is appropriate.

Setting quarterly reminders helps us keep track of our savings and the account's performance. It's also an opportunity to make changes to our investments. 

At Archimedes, our goal is to make investment literacy accessible and free for everyone.

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