Employers do not have to contribute to a 401(k) in most cases. Federal law lets a company sponsor a traditional 401(k) without ever adding a dollar of its own money, and the plan document can label every employer contribution discretionary. That default flips in three specific situations: Safe Harbor 401(k) plans, SIMPLE IRAs, and any plan the IRS classifies as top-heavy. In those cases, the employer contribution stops being optional and becomes a legal requirement.
The Default Rule for Traditional 401(k) Plans
The Employee Retirement Income Security Act of 1974 sets minimum standards for private-sector retirement plans, but it does not require any company to offer one.1Legal Information Institute. ERISA When an employer does set one up, ERISA still does not force it to match employee deferrals or make any other contribution. The plan document decides, and the plan document is allowed to say contributions are entirely discretionary.
Discretionary means exactly what it sounds like. An employer can match 50% of employee deferrals one year, drop to 25% the next, and skip matching entirely the year after that. The IRS permits non-elective contributions for all participants, profit-sharing contributions tied to company performance, or no contributions at all.2Internal Revenue Service. Retirement Topics – Contributions Federal oversight focuses on fiduciary duty and plan administration, not on forcing the employer to fund accounts.
This is why your Summary Plan Description matters. Read it. If the document commits to a specific formula, the employer is bound to it. If it uses the word discretionary, assume nothing is guaranteed from year to year.
When Employer Contributions Are Legally Required
Three plan situations override the discretionary default. Each has its own formula and its own trigger.
Safe Harbor 401(k) Plans
An employer that adopts a Safe Harbor 401(k) commits to a specific contribution every year. In exchange, the IRS lets the plan skip the non-discrimination testing that traditional plans have to pass. Three formulas qualify:
- The basic match. The employer matches 100% of the first 3% of pay an employee defers, plus 50% of the next 2%. An employee who contributes at least 5% of salary receives the equivalent of a 4% match.
- An enhanced match. The formula must be at least as generous as the basic match at every tier and cannot require employees to defer more than 6% of pay to get the full match. A dollar-for-dollar match on the first 6% of pay is a common example.
- A non-elective contribution. At least 3% of each eligible employee’s compensation, deposited whether or not the employee contributes anything.
All three formulas produce contributions that are 100% vested immediately.
SIMPLE IRA Plans
Businesses with 100 or fewer employees earning at least $5,000 in the prior year can sponsor a Savings Incentive Match Plan for Employees, known as a SIMPLE IRA.3U.S. Department of Labor. SIMPLE IRA Plans for Small Businesses There is no discretion. The employer must contribute every year, using one of two formulas:
- A dollar-for-dollar match up to 3% of compensation. An employee earning $50,000 who contributes $2,500 receives $1,500 from the employer. An employee who contributes nothing receives nothing.
- A 2% non-elective contribution for every eligible employee, whether or not the employee defers. For 2026, the compensation counted for this calculation is capped at $360,000.4Internal Revenue Service. COLA Increases for Dollar Limitations on Benefits and Contributions
These requirements live in the Internal Revenue Code, not the plan document. Skipping a year exposes the employer to plan disqualification.5Internal Revenue Service. Retirement Topics – SIMPLE IRA Contribution Limits
Under SECURE 2.0, employers may make additional non-elective contributions of up to 10% of each eligible employee’s compensation, capped at $5,000 per employee.6Internal Revenue Service. Miscellaneous Changes Under the SECURE 2.0 Act of 2022 That extra amount is voluntary. The base 3% match or 2% non-elective remains mandatory.
Top-Heavy Plans
A 401(k) becomes top-heavy under Internal Revenue Code Section 416 when more than 60% of total account balances belong to key employees.7Office of the Law Revision Counsel. 26 USC 416 – Special Rules for Top-Heavy Plans For 2026, a key employee is generally an officer earning more than $235,000, a more-than-5% owner, or a more-than-1% owner earning over $150,000.8Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs
Once a plan is top-heavy, the employer must contribute at least 3% of annual compensation for every non-key employee, even employees who chose not to defer any of their own pay.7Office of the Law Revision Counsel. 26 USC 416 – Special Rules for Top-Heavy Plans The one exception: if the highest contribution rate for any key employee is less than 3%, the employer can use that lower rate for everyone else.
The test runs each year using account balances on the determination date, which is the last day of the preceding plan year (or the last day of the first plan year for a brand-new plan).9eCFR. 26 CFR 1.416-1 – Questions and Answers on Top-Heavy Plans A small business can pass the test for years and then tip over the 60% threshold as owner balances grow faster than rank-and-file balances.
Receiving a Contribution Is Not the Same as Owning It
Your own deferrals are always 100% yours the moment they leave your paycheck. Employer money is different. Vesting rules decide how much of the employer’s contribution you actually keep if you leave the company.
For discretionary employer contributions in a traditional 401(k), federal law allows two vesting schedules:10Office of the Law Revision Counsel. 26 USC 411 – Minimum Vesting Standards
- Three-year cliff vesting. You own 0% of employer contributions until you complete three years of service, then jump straight to 100%. Leave at two years and eleven months and you forfeit all of it.
- Two-to-six-year graded vesting. Ownership climbs in steps: 20% after two years, 40% after three, 60% after four, 80% after five, and 100% after six.
Safe Harbor contributions and SIMPLE IRA employer contributions are 100% vested immediately, regardless of the formula the employer chose. Top-heavy minimum contributions follow whichever schedule the plan document specifies, but the plan has to use one of the two schedules above.
If you are weighing a job change and your employer makes discretionary contributions, check your vesting percentage before you give notice. A few extra months of service can be worth thousands of dollars.
What Happens if a Required Contribution Is Missed
Where the contribution is mandatory, missing it is a compliance failure, not a minor bookkeeping problem. The IRS can impose excise taxes, require correction, and in the worst case disqualify the plan.
For plans subject to minimum funding standards, the employer files Form 5330 and pays an initial excise tax of 10% of the unpaid required contributions.11Internal Revenue Service. Instructions for Form 5330 If the shortfall is not corrected by the end of the taxable period, an additional tax of 100% of the unpaid amount applies. That is the statutory number, not a typo.
For operational mistakes, such as failing to run a Safe Harbor match for some employees, the IRS offers a less punitive path through the Employee Plans Compliance Resolution System. The Self-Correction Program lets sponsors fix certain failures without contacting the IRS, provided they had reasonable compliance practices in place and correct the error promptly. Significant operational failures must be corrected within two years of the end of the plan year in which they occurred.12Internal Revenue Service. EPCRS Overview SIMPLE IRA sponsors are not eligible for Self-Correction and must use a different correction method.
Plan disqualification is the ceiling. Losing qualified status makes employer contributions non-deductible, can make employee deferrals immediately taxable, and strips the plan trust of its tax-exempt treatment. If your account is short a required employer contribution, the failure is the employer’s to fix, and both the IRS and the Department of Labor have procedures that generally push toward correction rather than plan termination.