{ "openapi": "3.1.0", "info": { "title": "estimatetax.net Tax Calculation API", "version": "1.0.0", "summary": "US federal, state and local income tax for the 2026 tax year.", "description": "A deterministic calculator for US income tax: federal brackets and FICA, all 50 states\nand the District of Columbia, and local income tax where counties, cities or school\ndistricts levy one.\n\nNo key, no signup, no request body required — a GET with an income and a state code is\nenough. CORS is open, so it can be called from a browser.\n\nEvery response carries the document each figure was read from and the date it was\nchecked, under `sources`. Nothing is estimated or interpolated: a figure either comes\nfrom a primary source or the endpoint does not return it.", "contact": { "name": "Pablo Ruiz Quintero", "url": "https://estimatetax.net/about/pablo-ruiz-quintero/" }, "license": { "name": "CC BY 4.0", "url": "https://creativecommons.org/licenses/by/4.0/" }, "termsOfService": "https://estimatetax.net/terms/" }, "servers": [ { "url": "https://estimatetax.net", "description": "Production" } ], "externalDocs": { "description": "API documentation and limits", "url": "https://estimatetax.net/api/" }, "tags": [ { "name": "calculation", "description": "Income tax calculation" } ], "paths": { "/api/v1/calculate": { "get": { "tags": [ "calculation" ], "operationId": "calculateGet", "summary": "Calculate income tax for one income and place", "description": "Rate limited to 60 requests per minute per IP. No authentication.", "parameters": [ { "name": "income", "in": "query", "required": true, "description": "Gross annual employment income, in US dollars.", "schema": { "type": "number", "minimum": 0, "examples": [ 100000 ] } }, { "name": "state", "in": "query", "required": false, "description": "Two-letter state code. Omit for federal only.", "schema": { "type": "string", "enum": [ "AL", "AK", "AZ", "AR", "CA", "CO", "CT", "DE", "DC", "FL", "GA", "HI", "ID", "IL", "IN", "IA", "KS", "KY", "LA", "ME", "MD", "MA", "MI", "MN", "MS", "MO", "MT", "NE", "NV", "NH", "NJ", "NM", "NY", "NC", "ND", "OH", "OK", "OR", "PA", "RI", "SC", "SD", "TN", "TX", "UT", "VT", "VA", "WA", "WV", "WI", "WY" ] } }, { "name": "filingStatus", "in": "query", "required": false, "schema": { "type": "string", "enum": [ "single", "married_jointly", "married_separately", "head_of_household" ], "default": "single" } }, { "name": "city", "in": "query", "required": false, "description": "Slug of the county, city or school district that levies a local income tax, for example \"allegany-county\" in MD or \"new-york-city\" in NY. Only meaningful in the eleven states with a local income tax.", "schema": { "type": "string", "examples": [ "allegany-county" ] } }, { "name": "preTaxDeductions", "in": "query", "required": false, "description": "Pre-tax deductions such as 401(k) or health premiums, in US dollars.", "schema": { "type": "number", "minimum": 0, "default": 0 } }, { "name": "selfEmploymentIncome", "in": "query", "required": false, "description": "Net self-employment income, taxed for both halves of FICA.", "schema": { "type": "number", "minimum": 0, "default": 0 } } ], "responses": { "200": { "description": "The calculation, with the source of every figure.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/Calculation" } } } }, "400": { "description": "Missing or invalid income, or an unknown state code.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/Error" } } } }, "429": { "description": "More than 60 requests in a minute from one IP." } } }, "post": { "tags": [ "calculation" ], "operationId": "calculatePost", "summary": "Same calculation, with the parameters in a JSON body", "requestBody": { "required": true, "content": { "application/json": { "schema": { "$ref": "#/components/schemas/Input" } } } }, "responses": { "200": { "description": "The calculation, with the source of every figure.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/Calculation" } } } }, "400": { "description": "Missing or invalid income, or an unknown state code.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/Error" } } } } } } } }, "components": { "schemas": { "Input": { "type": "object", "required": [ "income" ], "properties": { "income": { "type": "number", "minimum": 0 }, "state": { "type": "string", "enum": [ "AL", "AK", "AZ", "AR", "CA", "CO", "CT", "DE", "DC", "FL", "GA", "HI", "ID", "IL", "IN", "IA", "KS", "KY", "LA", "ME", "MD", "MA", "MI", "MN", "MS", "MO", "MT", "NE", "NV", "NH", "NJ", "NM", "NY", "NC", "ND", "OH", "OK", "OR", "PA", "RI", "SC", "SD", "TN", "TX", "UT", "VT", "VA", "WA", "WV", "WI", "WY" ] }, "filingStatus": { "type": "string", "enum": [ "single", "married_jointly", "married_separately", "head_of_household" ], "default": "single" }, "city": { "type": "string" }, "preTaxDeductions": { "type": "number", "minimum": 0, "default": 0 }, "selfEmploymentIncome": { "type": "number", "minimum": 0, "default": 0 } } }, "Bracket": { "type": "object", "description": "One federal bracket and how much of the taxable income fell in it.", "properties": { "rate": { "type": "number" }, "taxableInBracket": { "type": "number" }, "tax": { "type": "number" }, "min": { "type": "number" }, "max": { "type": "number" } } }, "Source": { "type": "object", "description": "The document a figure was read from, and when it was checked.", "properties": { "citation": { "type": "string" }, "authority": { "type": "string" }, "document": { "type": "string" }, "url": { "type": "string", "format": "uri" }, "verified": { "type": "string", "format": "date" }, "checked": { "type": "string", "format": "date" } } }, "Calculation": { "type": "object", "properties": { "taxYear": { "type": "integer", "examples": [ 2026 ] }, "input": { "$ref": "#/components/schemas/Input" }, "federal": { "type": "object", "properties": { "adjustedGrossIncome": { "type": "number" }, "deduction": { "type": "number" }, "taxableIncome": { "type": "number" }, "incomeTax": { "type": "number" }, "socialSecurity": { "type": "number" }, "medicare": { "type": "number" }, "additionalMedicare": { "type": "number" }, "selfEmploymentTax": { "type": "number" }, "totalFica": { "type": "number" }, "marginalRate": { "type": "number" }, "brackets": { "type": "array", "items": { "$ref": "#/components/schemas/Bracket" } } } }, "state": { "type": [ "object", "null" ], "properties": { "code": { "type": "string" }, "name": { "type": "string" }, "tax": { "type": "number" }, "system": { "type": "string", "enum": [ "graduated", "flat", "none" ], "description": "none means the state levies no income tax at all." } } }, "local": { "type": [ "object", "null" ], "description": "Present only where a county, city or school district levies its own.", "properties": { "jurisdiction": { "type": "string" }, "tax": { "type": "number" }, "rate": { "type": "number" }, "base": { "type": "string", "description": "What the local rate applies to: earned income, or state taxable income." } } }, "totals": { "type": "object", "properties": { "totalTax": { "type": "number" }, "netIncome": { "type": "number" }, "effectiveRate": { "type": "number" }, "effectiveIncomeTaxRate": { "type": "number" } } }, "sources": { "type": "object", "description": "Where each layer of the calculation came from.", "properties": { "federal": { "$ref": "#/components/schemas/Source" }, "state": { "$ref": "#/components/schemas/Source" }, "local": { "$ref": "#/components/schemas/Source" } } }, "disclaimer": { "type": "string" } } }, "Error": { "type": "object", "properties": { "error": { "type": "string" } } } } }, "x-tax-year": 2026, "x-federal-source": { "citation": "IRS Rev. Proc. 2025-32, § 3.01, Tables 1-4", "verified": "2026-08-31" }, "x-jurisdictions": { "states": 51, "note": "50 states and the District of Columbia" } }