Retirement

Solo 401(k) vs SEP-IRA contribution sizing (self-employed)

Sizes the maximum retirement contribution for a self-employed person (sole proprietor / single-member LLC) under both a SEP-IRA and a solo 401(k) from Schedule C net profit. It applies the self-employment-tax adjustment (net profit − ½ SE tax = plan compensation) and the self-employed "reduced rate" (a 25% employer plan is 20% of plan compensation), adds the solo 401(k) employee elective deferral plus the age catch-up, and caps everything at the §415(c) annual-additions limit. Returns both plan totals and which lets you save more. Deterministic; not tax advice.

post/v1/retirement/self-employed

Request

  • Base URL: https://api.numeratica.com
  • URL: https://api.numeratica.com/v1/retirement/self-employed
  • Auth: one of:
    • HTTP bearer
    • API key in header X-API-Key

Request body

tax_yearinteger

Omit for 2026.

ageinteger required

Drives the 401(k) catch-up.

net_profitnumber required

Schedule C net profit (before the retirement contribution).

existing_w2_deferralsnumber

Elective deferrals already made this year to another employer's 401(k)/403(b) (per-person §402(g) limit).

Response

The contribution sizing

result_idstring
engine_versionstring
disclaimerstring

Example response

{
  "result_id": "seretire_1a2b3c4d5e6f7a8b",
  "engine_version": "self-employed-retirement-1.0.0"
}

Changes

No recorded changes to this operation across all 1 revision of this API.