---
title: "Gross-to-Net Payroll Calculator (FICA)"
method: POST
path: "/v1/tools/compute_gross_to_net"
tags: ["TODO_TAGS_REVIEW", "TODO_AP2_EXPORT_REVIEW"]
---

# Gross-to-Net Payroll Calculator (FICA)

`POST /v1/tools/compute_gross_to_net`

## Request

- Base URL: `https://ainumbers.co`
- URL: `https://ainumbers.co/v1/tools/compute_gross_to_net`
- Auth: none declared

Gross-to-net payroll calculation: FICA (Social Security 6.2% up to the OASDI contribution and benefit base for the selected tax year, Medicare 1.45% uncapped, Additional Medicare Tax 0.9% on cumulative wages over $200,000 per IRC 3101(b)(2)), pretax deduction ordering (401(k)/HSA/Section 125 reduce both FICA and federal-taxable wages), and net pay. tax_year is a required input and selects the wage base: $184,500 for 2026 and $176,100 for 2025, with an absent or unsupported year failing closed with error unsupported_or_missing_tax_year rather than defaulting. The Social Security and Medicare rates and the $200,000 Additional Medicare threshold are statutory and not indexed, so they are not year-keyed. federal_withholding_per_period is a declared input, normally fed from art-338-compute-federal-withholding's output at the same tax_year, since kernels cannot import one another. Federal only, not tax advice, state withholding and state payroll taxes out of scope. Consumes art-338-compute-federal-withholding. Not compute_federal_withholding itself, which only computes the federal income tax withholding line.

**Tool URL:** https://ainumbers.co/chaingraph/art-339-compute-gross-to-net.html

## Request body

- object
  - `federal_withholding_per_period` number
  - `gross_wages_per_period` number
  - `post_tax_other_deductions` number
  - `pretax_reduces_fica_and_fit` number
  - `tax_year` unknown, required
  - `ytd_fica_wages_before_period` number

## Response `200`

Successful tool execution result

- object
  - `additional_medicare_tax` integer
  - `additional_medicare_threshold` integer
  - `additional_medicare_wages_this_period` integer
  - `constants_version` string
  - `error` string
  - `federal_withholding_per_period` integer
  - `fica_tax_total` number
  - `fica_wages_this_period` integer
  - `medicare_tax` number
  - `net_pay` number
  - `note` string
  - `post_tax_other_deductions` integer
  - `pretax_reduces_fica_and_fit` integer
  - `regulatory_basis` string
  - `social_security_tax` integer
  - `ss_taxable_wages_this_period` integer
  - `ss_wage_base` integer
  - `supported_tax_years` string[]
  - `tax_year` string
  - `ytd_fica_wages_after_period` integer

---

[API](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite.md) · [All operations](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/llms.txt) · [OpenAPI document](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/revisions/b462e4f5bb28?raw)