Reference

API reference

Generated from the live OpenAPI 3.1 document (version 2026-10-01). Base URL:

https://tax-api-dev.itensiahr.com/v1

Endpoints

GET /rates/lookup — Look up every tax for a paycheck
GET /jurisdictions — List jurisdictions and their tax programs
GET /jurisdictions/{code} — All taxes in force for one jurisdiction
GET /versions/{id} — One published (or superseded) version, by id
GET /changes — Change feed (Starter plan and up)
GET /status — Service status and data freshness
GET /openapi.json — This specification

Look up every tax for a paycheck

GET/rates/lookup

Returns all federal taxes plus the work state's taxes (and the residence state's income tax withholding if different) in force on `pay_date`. Taxes without a published version for that date are listed in `meta.unavailable` — never silently omitted.

Parameter	Type	Description
`work_state`required	query · string	Two-letter state where the work is performed
`pay_date`	query · string (date)	Defaults to today (UTC)
`residence_state`	query · string	Employee's resident state, if different
`filing_status`	query · string	Filters per-status values and brackets (single, married_joint, head_of_household, …)
`include`	query · string	Comma list: federal, state
`as_of`	query · string (date-time)	Answer exactly as the API would have at this moment (Growth plan and up)

Responses: 200 Taxes in force · 400 Invalid parameter · 401 Missing or invalid API key · 402 Trial ended · 403 Account suspended, or the feature is not in your plan (PLAN_FEATURE) · 404 Not found · 429 Rate limit (RATE_LIMITED) or monthly quota (QUOTA_EXCEEDED) reached

List jurisdictions and their tax programs

GET/jurisdictions

Responses: 200 Jurisdictions · 400 Invalid parameter · 401 Missing or invalid API key · 402 Trial ended · 403 Account suspended, or the feature is not in your plan (PLAN_FEATURE) · 404 Not found · 429 Rate limit (RATE_LIMITED) or monthly quota (QUOTA_EXCEEDED) reached

All taxes in force for one jurisdiction

GET/jurisdictions/{code}

Parameter	Type	Description
`code`required	path · string	US for federal, or a state code
`date`	query · string (date)

Responses: 200 Jurisdiction taxes · 400 Invalid parameter · 401 Missing or invalid API key · 402 Trial ended · 403 Account suspended, or the feature is not in your plan (PLAN_FEATURE) · 404 Not found · 429 Rate limit (RATE_LIMITED) or monthly quota (QUOTA_EXCEEDED) reached

One published (or superseded) version, by id

GET/versions/{id}

Parameter	Type	Description
`id`required	path · string

Responses: 200 Version · 400 Invalid parameter · 401 Missing or invalid API key · 402 Trial ended · 403 Account suspended, or the feature is not in your plan (PLAN_FEATURE) · 404 Not found · 429 Rate limit (RATE_LIMITED) or monthly quota (QUOTA_EXCEEDED) reached

Change feed (Starter plan and up)

GET/changes

Versions published or superseded since a timestamp. Poll it daily, or after each payroll run.

Parameter	Type	Description
`since`	query · string (date-time)	Defaults to 30 days ago

Responses: 200 Changes · 400 Invalid parameter · 401 Missing or invalid API key · 402 Trial ended · 403 Account suspended, or the feature is not in your plan (PLAN_FEATURE) · 404 Not found · 429 Rate limit (RATE_LIMITED) or monthly quota (QUOTA_EXCEEDED) reached

Service status and data freshness

GET/status

No authentication

Responses: 200 Status

This specification

GET/openapi.json

No authentication

Responses: 200 OpenAPI document

Schemas

`Meta`

Field	Type	Description
`request_id`	string
`processing_ms`	integer
`api_version`	string

`Bracket`

Field	Type	Description
`table`	string
`filing_status`	string
`period`	string
`over`	string
`not_over`	string \| null
`rate`	string
`base_tax`	string

`Tax`

Field	Type	Description
`tax_code`	string
`tax_type`	string
`name`	string
`jurisdiction`	object
`applies_to`	federal \| work \| residence
`rate_structure`	string
`effective_from`	string (date)
`effective_to`	string,null (date)	Exclusive end: the first date this version no longer applies. null while open-ended.
`tax_year`	integer
`parameters`	object
`brackets`	array of Bracket
`notes`	string \| null
`version`	object
`sources`	array of object

`LookupResponse`

Field	Type	Description
`data`	object
`meta`

`Jurisdiction`

Field	Type	Description
`code`	string
`state`	string \| null
`name`	string
`level`	string
`has_wage_income_tax`	boolean
`taxes`	array of object

`Error`

Field	Type	Description
`error`	object