Last Updated 1/29/2026
If you are a client of My Solo 401k Financial and used Fidelity Investments for the non-prototype brokerage accounts for the solo 401k, this procedure describes how to:
- make employer Roth solo 401k contributions to the Fidelity Investments non-prototype brokerage account that has been labeled as “Roth”;
- report the Roth solo 401k employer contribution on your Form 1120-S corporate tax return line 17 if your self-employed business is taxed as an S-corp;
- report the Roth solo 401k employer contribution as a taxable in-plan conversion on Form 1099-R; reason being, Roth solo 401k employer contributions are first reported as tax deductible contributions for the year for which the contributions are made and then reported as taxable for the year in which the contributions are deposited by issuing a Form 1099-R and reporting the amount on Line 5a and 5b of Form 1040.
Step 1: Make the employer Roth solo 401k contribution to the Fidelity Investments brokerage account for the solo 401k that is labeled “ROTH”.
You can make the contribution electronically via ACH by linking your bank account to the Fidelity brokerage account. See the following:
- ACH in – Click here to see special instructions. You can make your Solo 401k annual contribution into the Fidelity non-prototype account via ACH or by physical check. ACH transfers are set up on your bank side.
Step 2: Complete the on-line conversion form.
After you make the employer Roth solo 401k contribution, we will need to issue a Form 1099-R to report it as a taxable conversion, so make sure to complete the following form once you have made the contribution. https://www.mysolo401k.net/pretax-to-roth-solo-401k-in-plan-conversion-form/
Important Note 1: For employer Roth solo 401k contributions made in 2026 for 2025 by the business tax return due date plus extension, the contribution is reported on your 2025 business tax return; however, it will be reported as taxable in 2026 so a Form 1099-R will be issued in by February of 2027 provided you timely submit the above on-line conversion form. Reason being, Roth solo 401k employer contributions are first reported as tax deductible contributions for the year for which the contributions are made and then reported as taxable for the year in which the contributions are deposited by issuing a Form 1099-R and reporting the amount on Line 5a and 5b of the 2026 Form 1040 which is due to the IRS in April of 2027.
Important Note 2: For employer Roth solo 401k contributions made in 2026 for tax year 20265, the contribution will be reported as tax deductible on your 2026 business tax return(e.g., Form 1120-S if your business is taxed as an S-corp.), and as taxable on the 2026 Form 1099-R that is issued by February of 2027.
More Information:
See also the following for more information.
For a self-employed business taxed as an S-corp., how to report employer Roth solo 401k contributons on Form 1120-S: https://www.mysolo401k.net/how-do-i-report-employer-roth-solo-401k-contributions-on-my-s-corp-tax-return-1120s-401k-roth/
