The required minimum distribution is not required for a particular calendar year if the account owner is employed by the employer during the entire calendar year and the account owner does not own more than 5% of the employer's business at any point during the calendar year.[a][20][21] Required minimum distributions apply to both traditional contributions and Roth contributions to a 401(k) plan.
A recent study from the Investment Company Institute found that more than 80 percent of those surveyed had rolled over their entire balance in their most recent IRA rollover. However, one of the unique things about an IRA rollover is that you do a partial IRA rollover to move just part of an account. However, you must still meet eligibility requirements and follow IRA rollover rules.
To help ensure that companies extend their 401(k) plans to low-paid employees, an IRS rule limits the maximum deferral by the company's highly compensated employees (HCEs) based on the average deferral by the company's non-highly compensated employees (NHCEs). If the less compensated employees save more for retirement, then the HCEs are allowed to save more for retirement. This provision is enforced via "non-discrimination testing". Non-discrimination testing takes the deferral rates of HCEs and compares them to NHCEs. In 2008, an HCE was defined as an employee with compensation greater than $100,000 in 2007, or as an employee that owned more than 5% of the business at any time during the year or the preceding year.[32] In addition to the $100,000 limit for determining HCEs, employers can elect to limit the top-paid group of employees to the top 20% of employees ranked by compensation.[32] That is, for plans with the first day of the plan-year in the 2007 calendar year, HCEs are employees who earned more than $100,000 in gross compensation (also known as 'Medicare wages') in the prior year. For example, most testing done in 2009 was for the 2008 plan-year, which compared 2007 plan-year gross compensation to the $100,000 threshold in order to determine who was an HCE and who was an NHCE. The threshold was $125,000 for 2019, and is $130,000 for 2020.[28]
If you’re no longer employed by the employer maintaining your retirement plan and your plan account is between $1,000 and $5,000, the plan administrator may deposit the money into an IRA in your name if you don’t elect to receive the money or roll it over. If your plan account is $1,000 or less, the plan administrator may pay it to you, less, in most cases, 20% income tax withholding, without your consent. You can still roll over the distribution within 60 days.
There are a number of "safe harbor" provisions that can allow a company to be exempted from the ADP test. This includes making a "safe harbor" employer contribution to employees' accounts. Safe harbor contributions can take the form of a match (generally totaling 4% of pay) or a non-elective profit sharing (totaling 3% of pay). Safe harbor 401(k) contributions must be 100% vested at all times with immediate eligibility for employees. There are other administrative requirements within the safe harbor, such as requiring the employer to notify all eligible employees of the opportunity to participate in the plan, and restricting the employer from suspending participants for any reason other than due to a hardship withdrawal.

Automatic 401(k)s are designed to encourage high participation rates among employees. Therefore, employers can attempt to enroll non-participants as often as once per year, requiring those non-participants to opt out each time if they do not want to participate. Employers can also choose to escalate participants' default contribution rate, encouraging them to save more.[34]

If you withdraw funds from an IRA, and then subsequently redeposit them to your IRA within 60 days, the transaction would not be taxed. You can only do this type of IRA transfer once in any 12 month time period. This one-per-year provision does not apply to trustee-to-trustee transfers where the money is sent directly from one institution to another.
Even though the term "401(k)" is a reference to a specific provision of the U.S. Internal Revenue Code section 401, it has become so well known that it has been used elsewhere as a generic term to describe analogous legislation. For example, in October 2001, Japan adopted legislation allowing the creation of "Japan-version 401(k)" accounts even though no provision of the relevant Japanese codes is in fact called "section 401(k)".[41][42][43]

Using a Roth IRA conversion requires investors to follow strict rules like paying taxes and completing the conversion within 60 days. For investors who want to roll money from a tax-deferred account into a Roth IRA, it’s a good idea to work with an accountant or licensed financial advisor. Otherwise, investors may end up paying taxes on the converted amount and/or a 10 percent penalty.

There is a maximum limit on the total yearly employee pre-tax or Roth salary deferral into the plan. This limit, known as the "402(g) limit", was $19,000 for 2019, and is $19,500 for 2020.[27] For future years, the limit may be indexed for inflation, increasing in increments of $500. Employees who are at least 50 years old at any time during the year are now allowed additional pre-tax "catch up" contributions of up to $6,000 for 2015–2019, and $6,500 for 2020.[28][27] The limit for future "catch up" contributions may also be adjusted for inflation in increments of $500. In eligible plans, employees can elect to contribute on a pre-tax basis or as a Roth 401(k) contribution, or a combination of the two, but the total of those two contributions amounts must not exceed the contribution limit in a single calendar year. This limit does not apply to post-tax non-Roth elections.

A 401(k) plan may have a provision in its plan documents to close the account of former employees who have low account balances. Almost 90% of 401(k) plans have such a provision.[24] As of March 2005, a 401(k) plan may require the closing of a former employee's account if and only if the former employee's account has less than $1,000 of vested assets.
In order to be eligible to receive a QCD, a qualified charitable organization must meet requirements under section 501(c)(3) of the Internal Revenue Code. Qualifying organizations must be involved in religious, charitable, educational or literary endeavors, or, the prevention of cruelty to animals and children, fostering amateur sports competitions (locally and internationally), testing for public safety or scientific activities or operations.
Account owners must begin making distributions from their accounts by April 1 of the calendar year after turning age 70 1/2 or April 1 of the calendar year after retiring, whichever is later.[15] The amount of distributions is based on life expectancy according to the relevant factors from the appropriate IRS tables.[16] For individuals who attain age 70 1/2 after December 31, 2019, distributions are required by April 1 of the calendar year after turning age 72 or April 1 of the calendar year after retiring, whichever is later.[17]