Changing jobs mid-year is one of the most common ways people accidentally mess up their 401k contributions. Your new employer has no idea what you contributed at your old job, and if you don't coordinate carefully, you can over-contribute, lose employer match, or miss out on valuable after-tax contribution space.

This guide covers exactly what happens to your 401k limits when you switch employers, how to avoid costly mistakes, and how to take advantage of the per-employer 415(c) limit.

The Two Limits: One Shared, One Per Employer

The IRS sets two separate limits on 401k contributions. Understanding which one is shared and which one resets is the key to navigating a mid-year job change.

The Over-Contribution Risk

Here is the most common mistake: your new employer's payroll system has no way to know what you contributed at your previous job. When you enroll in the new plan, it treats you as if you're starting from zero. If your old job already used up a chunk of the $24,500.00 elective deferral limit, you need to manually track your remaining room and adjust your new contribution percentages accordingly.

If you exceed the $24,500.00 limit across both employers, the IRS requires you to withdraw the excess by April 15 of the following year. The excess contribution (plus any earnings on it) gets added to your taxable income. If you miss the deadline, the excess is taxed twice: once in the year of contribution and again when you withdraw it in retirement.

Let's Walk Through an Example

Let's walk through a realistic scenario to see exactly how the numbers work.

The Setup

• Job A: You leave at the end of June. By that point, you've contributed $15,000.00 in elective deferrals (pre-tax and Roth combined).
• Job B: You start in July with a $180,000.00 salary, paid biweekly. The plan auto-enrolls you at 10% pre-tax. There are 13 biweekly paychecks remaining in the year.

What Happens If You Don't Adjust

Each biweekly paycheck at Job B is $6,923.08 gross. At 10% deferral, that is $692.31 per paycheck in elective contributions.

In this scenario, you would end up just under the limit at roughly $24,000.00. But if Job A had contributed $18,000.00 instead, the combined total would hit $27,000.00, putting you $2,500.00 over the limit.

How to Calculate Your Remaining Elective Room

Before you set your contribution percentages at your new job, do this simple calculation:

1. Get your year-to-date elective contribution total from your last pay stub at your old employer (or request it from HR).
2. Subtract that from $24,500.00. That is your remaining elective room.
3. Divide your remaining room by the number of paychecks left in the year at your new job. That gives you the dollar amount per paycheck.
4. Convert that dollar amount to a percentage of your gross pay per paycheck. Set your pre-tax or Roth deferral to that percentage.

The Upside: Per-Employer 415(c) Limits

While the elective deferral limit is shared and requires careful tracking, the $72,000.00 total additions limit (415(c)) is per employer. This is actually a significant advantage if either or both of your employers support after-tax contributions and in-plan Roth conversions.

With two qualifying employers in the same year, you could theoretically have access to up to $144,000.00 in total 415(c) space. After subtracting the shared $24,500.00 elective limit and both employer matches, the remaining room is available for mega backdoor Roth contributions.

That is $109,000.00 in combined after-tax room across both jobs. Even if you only used a fraction of that at each employer, the per-employer bucket is a powerful tool. Read more about this strategy in the mega backdoor Roth guide.

401k Rollover Options

When you leave an employer, you have several options for the money in your old 401k plan:

• Leave it in the old plan. Most plans allow this if your balance exceeds $5,000.00. This is the simplest option, but you will have multiple accounts to track and may face limited investment options or higher fees.
• Roll it into your new employer's plan. This consolidates your accounts and keeps the money in a 401k, which preserves certain protections (like creditor protection and access to plan loans). Not all plans accept incoming rollovers, so check with your new employer.
• Roll it into an IRA. A traditional 401k rolls into a traditional IRA; Roth 401k rolls into a Roth IRA. IRAs typically offer a wider range of investment options and lower fees. However, if you plan to do a backdoor Roth IRA conversion, having a traditional IRA balance triggers the pro-rata rule, which complicates things.
• Cash it out. This triggers income tax plus a 10% early withdrawal penalty if you are under 59.5. Almost never the right choice.

Vesting Schedules: What You Might Lose

Your own contributions (pre-tax, Roth, and after-tax) are always 100% vested. You keep every dollar. But employer match contributions typically follow a vesting schedule, and leaving before you are fully vested means forfeiting some or all of the match.

Common vesting schedules include:

• Immediate vesting: You keep 100% of the match from day one. More common at tech companies.
• Cliff vesting: 0% vested until a specific date (typically 3 years), then 100%. If you leave at 2 years and 11 months, you lose the entire match.
• Graded vesting: Vesting increases gradually (e.g., 20% per year over 5 years). You keep whatever percentage you have earned by your departure date.

Before accepting a new job offer, check your current vesting schedule. If you are close to a vesting cliff, it may be worth negotiating your start date or asking the new employer to compensate for the lost match via a signing bonus.

Employer Match at the New Job

Some employers require a waiting period before you are eligible for the 401k plan or for the employer match. Common waiting periods range from 30 days to 12 months. If you start in July and the plan has a 90-day waiting period, you will not begin receiving match until October.

Factor this into your contribution strategy. During the waiting period, you are still consuming your remaining elective room without getting any match. If the match eligibility starts later, you may want to hold off on maxing your deferral until the match kicks in, so you do not front-load your contributions into a period with no match.

Putting It All Together

Here is the checklist for managing your 401k when changing jobs mid-year:

1. Get your year-to-date elective deferral total from your last pay stub at the old employer.
2. Calculate your remaining elective room ($24,500.00 minus what you already contributed).
3. Set your new employer contribution percentages to use your remaining room evenly across remaining paychecks.
4. Check if either employer supports after-tax contributions for mega backdoor Roth. Remember, each employer has its own $72,000.00 bucket.
5. Decide what to do with the old 401k: leave it, roll to the new plan, or roll to an IRA.
6. Check the vesting schedule at your old job and the eligibility waiting period at your new job.

Pre-Tax, Roth, or After-Tax?

A job change is also a good time to reconsider your contribution type. If your income is changing significantly, the optimal split between pre-tax and Roth may shift. For a detailed breakdown of when each type makes sense, see the pre-tax vs Roth vs after-tax guide.

Model Your Job Change

The numbers above are general guidelines. Your actual contribution strategy depends on your salary at each job, pay frequency, start and end dates, employer match formulas, vesting schedules, and whether your plans support after-tax contributions. Run the Numbers models all of this at the paycheck level, tracking the shared elective limit across multiple employers automatically.

Add both jobs, set their start and end months, configure each plan's match and contribution phases, and the simulator will show you exactly where the limits land and how to optimize your strategy.