How are solo 401k contributions accounted and reported?

Although solo 401(k) contributions are accounted for by depositing them into the solo 401k bank or brokerage account (i.e., you are not required to complete a contribution form), they are reported on your personal and business tax returns.

Watch: This is how solo 401k reporting applies

To learn how to report solo 401k contributions, which is based on how your self-employed business is taxed, see the following breakdown for each self-employed business entity type.

If the business is a sole proprietorship or an LLC taxed as a sole proprietorship:

If the business is a partnership or an LLC taxed as a partnership:

If the business is a C-Corporation, S-Corporation or an LLC taxed as an S-Corporation:

 

QUESTION:  FICA  & Income Taxes

For an S-Corp owner to make a $70k contribution to a 401k, they only need to make a wage of $70k to do so. If that is the case, how are the FICA and income taxes paid? Especially if someone is doing all Roth contributions so the income is taxable?

It seems that the wage would need to at least be enough to pay the FICA taxes, for example a 76k wage, pay fica taxes of nearly $6k, leaving $70k left over to make the 401k contribution.

If you know of some other way to avoid paying the employee side of the FICA out of the wage, please let me know.

ANSWER:

In short, don’t have to gross up W-2 wages to account for payroll taxes since ability to make solo  401k contributions when the self-employed business is taxed as an S-corp. or C-cor0. is based on W-2 wages before payroll taxes and don’t have to contribute via payroll so practically no need to gross up.

QUESTION:  FICA Tax

Does FICA apply to Solo 4o1k contributions where the self-employed business is taxed as an S-corporation or C-corporation.

ANSWER:

FICA applies to employee and voluntary after-tax solo 401k contributions but not to employer contributions. Click here to learn more.

2024 & 2025 Solo 401k Contribution Guides-Deep Dive

Sole Proprietorship, Independent Contractor,  Schedule C, LLC Taxed as Sole Proprietorship, 1099-NEC Independent Contractor

S-corp., C-corp., LLC Taxed as S-corp., W-2

Partnership, LLC Taxed as Partnership (Form 1065-K)

2024 & 2025 Mega Backdoor Roth Solo 401k Guides- Deep Dive

Partnerships, LLC taxed as Partnership

S-corp., C-corp., LLC taxed as S-corp., W-2

Sole Proprietorship, Singe Member LLC or 1099-MISC NECT Contractor

Guides 2023 & 2024-How Much Income Do I need to Max Out Solo 401k Contributions?

S-corp., C-corp., LLC taxed as S-corp., W-2

  • For Slides, CLICK HERE
  • For Video, CLICK HERE

Sole Proprietorship, Singe Member LLC or 1099-MISC NECT Contractor

  • For Slides, CLICK HERE
  • For Video, CLICK HERE

Partnerships, LLC taxed as Partnership

  • For Slides, CLICK HERE
  • For Video, CLICK HERE

Guides 2025 How Much Income Do I need to Max Out Solo 401k Contributions?

S-corp., C-corp., LLC taxed as S-corp., W-2

Sole Proprietorship, Singe Member LLC or 1099-MISC NECT Contractor

Partnerships, LLC taxed as Partnership

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