How to Fill Out the Schwab Solo 401(k) Contribution Transmittal Form

The Schwab Solo 401(k) contribution transmittal form is the one-page document that tells Charles Schwab how to classify money you are moving into your Individual 401(k): employee deferral or employer profit-sharing, traditional or Roth, current year or prior year. You can download it from Schwab’s forms library at schwab.com/resource/contribution-transmittal-form. Every deposit needs one. If you leave the classification fields blank, Schwab defaults the entire deposit to a traditional employee salary deferral, which may not be what you intended.1Charles Schwab. Individual 401(k) Plan – Traditional and Roth

What to Have Ready Before You Open the Form

Pull these together first. The form is short, but it asks for things that live in different places.

  • Your Schwab plan account number. This identifies the trust account receiving the funds and is different from any personal brokerage account number you hold at Schwab. It appears on your plan statements.
  • Your plan trust’s EIN. The Solo 401(k) trust has its own Employer Identification Number, separate from the EIN your business uses for payroll or income tax. If you never obtained a trust EIN (selected as “Employer Plan (401K, Money Purchase Plan, etc.)” when applying through the IRS), you will need one before Schwab can process certain plan transactions.
  • The dollar amount for each contribution type. Know the split between employee deferrals and employer profit-sharing, and within each, how much is traditional versus Roth. Schwab will not calculate limits for you.
  • The tax year the contribution applies to. Current year or prior year. Prior-year is common early in the calendar year when you are still inside the filing window.
  • The funding source. If you have a linked Schwab brokerage account you can fund internally; otherwise, you will write a check from your business bank account or arrange an external transfer.

Filling Out Each Section

The form is one page with a few labeled sections. Enter the plan account number and the plan trust’s EIN at the top. The rest is a series of checkboxes and a dollar amount.

Contribution Type: Employee vs. Employer, Traditional vs. Roth

Checkboxes separate employee elective deferrals from employer profit-sharing. Within employee deferrals, you also designate each dollar as traditional (pre-tax) or Roth (after-tax). Traditional deferrals reduce your taxable income for the contribution year. Roth deferrals do not reduce current taxable income, but qualified distributions in retirement come out tax-free.2Office of the Law Revision Counsel. 26 U.S. Code 402A – Optional Treatment of Elective Deferrals as Roth Contributions

This is the field that matters most. A blank designation defaults to traditional employee salary deferral, and fixing a misclassification after the fact is harder than checking the right box the first time.1Charles Schwab. Individual 401(k) Plan – Traditional and Roth

Starting in 2025, Schwab’s Individual 401(k) also allows employer profit-sharing contributions to be designated as Roth, an option created by Section 604 of the SECURE 2.0 Act for matching and nonelective employer contributions. If you choose it on the transmittal form, those employer Roth contributions get reported on Form 1099-R for the year they hit your account.3Internal Revenue Service. SECURE 2.0 Act Changes Affect How Businesses Complete Forms W-2

Tax Year

A separate checkbox asks whether the deposit applies to the current calendar year or the prior tax year. Use the prior-year option for contributions made between January 1 and your tax filing deadline that you want to count toward the previous year. The box controls how Schwab reports the contribution to the IRS, so an error here flows directly through to your tax return.

Dollar Amount and Signature

Write the total dollar amount. It has to match the check you are enclosing or the transfer amount you are requesting; a mismatch delays processing while Schwab reconciles the difference. The plan trustee or authorized employer representative signs and dates the form. In most Solo 401(k) setups, that is you.

Submitting the Form and Moving the Money

Schwab offers three channels, and they are not interchangeable.

Mail

Print and sign the form, then mail it with a check from your business account to Schwab Retirement Plan Services, PO Box 2026, Omaha, NE 68103-2026. For UPS or FedEx overnight, use the physical street address printed on the form’s instruction page or listed at workplace.schwab.com/contact-us. If you are mailing a large contribution close to a deadline, pay for tracked delivery; proof of the postmark is what protects your tax-year designation.

Fax

Fax the signed form to the number printed on the form. Faxing works when you are funding with an existing Schwab account balance rather than enclosing a check. Keep the transmission confirmation.

Phone

This is the route most Solo 401(k) holders actually use for electronic contributions. Schwab’s online platform does not currently support self-service Solo 401(k) deposits, because the system cannot sort employee from employer dollars or assign the correct tax year without a person on the other end. Call Schwab’s retirement plan support at 800-435-4000, or use the chat feature inside your account. A representative can move funds from your linked Schwab brokerage account into the Solo 401(k) during the call, classify the contribution type and tax year, and the money typically appears in the retirement account within minutes.1Charles Schwab. Individual 401(k) Plan – Traditional and Roth Have the completed transmittal form in front of you so you can read the details to the representative. They may ask you to fax or upload the signed form afterward for their records.

Deadlines That Control the Tax Year Box

Which tax year you can check on the form depends on when the money and the form arrive at Schwab.

  • Employee salary deferrals for a sole proprietor are due by the business’s tax filing deadline, including extensions. For a calendar-year filer, that is April 15, or October 15 with an extension. The written salary deferral election itself, though, must be made by the end of the plan year — December 31 for calendar-year plans.
  • Employer profit-sharing contributions are also due by the business’s tax filing deadline, including extensions.
  • To contribute both employee and employer dollars for a given tax year, a sole proprietor must have established the plan by the regular tax filing deadline (typically April 15). A plan set up after that date but before the extended deadline is limited to employer profit-sharing contributions for that year — no employee deferrals.
  • For S-corporation owners, employee deferrals generally must be made by December 31 of the plan year, while employer profit-sharing contributions follow the corporate filing deadline including extensions.4Internal Revenue Service. One-Participant 401(k) Plans

A Note on Contribution Limits

The form takes the dollar amount you write and sends it through. It does not check whether you are within the IRS annual limits, and Schwab will not catch an over-contribution for you. Before you fill in the amount, confirm your figure against the current year’s elective deferral ceiling, the combined employee-plus-employer ceiling, and any catch-up amount you qualify for. For sole proprietors and single-member LLCs, the employer piece is based on net self-employment earnings after adjustments, and the IRS provides a rate table and deduction worksheet in Chapter 5 of Publication 560 that handles the circular calculation.5Internal Revenue Service. Calculating Your Own Retirement Plan Contribution and Deduction Run those numbers first, then put the result on the transmittal form.