0s and 1s

0s and 1s CIS API

The CIS API from 0s and 1s — 7 operation(s) for cis.

GitHub OpenAPI

Operations 14

GET /api/v1/deduction CIS deduction, gross to net #
POST /api/v1/deduction CIS deduction, gross to net #
GET /api/v1/gross-up CIS gross up, net to gross #
POST /api/v1/gross-up CIS gross up, net to gross #
GET /api/v1/tax-month CIS tax month and deadlines #
POST /api/v1/tax-month CIS tax month and deadlines #
GET /api/v1/late-penalties CIS late filing penalties #
POST /api/v1/late-penalties CIS late filing penalties #
GET /api/v1/gross-payment-turnover-test CIS gross payment status turnover test #
POST /api/v1/gross-payment-turnover-test CIS gross payment status turnover test #
GET /api/v1/needs-verification Does a CIS subcontractor need verifying? #
POST /api/v1/needs-verification Does a CIS subcontractor need verifying? #
GET /api/v1/nil-return-check Is a CIS nil return due? #
POST /api/v1/nil-return-check Is a CIS nil return due? #

Specifications

⚙
OpenAPI
https://artifacts.apis.io/0sand1s-co-uk/openapi/0sand1s-co-uk-cis-api-openapi.yml

Schemas & Data

📊
JSONSchema
https://artifacts.apis.io/0sand1s-co-uk/json-schema/0sand1s-co-uk-tool-response-schema.json

Other Resources

🔗
APIsJSON
https://artifacts.apis.io/0sand1s-co-uk/apis.yml

Work with this as data

Every API here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for apis

7 MCP tools reach this
  • find_apisBrowse and filter every API in the catalog.
  • get_api_artifactsOne API's artifacts, grouped by type.
  • get_openapiThe primary OpenAPI for this API.
  • find_similar_apisAPIs that look like this one.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

curl for this page
This API 
curl "https://apis.io/api/v1/apis/0sand1s-co-uk:0sand1s-co-uk-cis-api"
All apis 
curl "https://apis.io/api/v1/apis?limit=25"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.

OpenAPI Specification

0sand1s-co-uk-cis-api-openapi.yml Raw ↑ 
openapi: 3.2.0
info:
  title: 0s and 1s CIS API
  version: 1.0.1
  description: 'Free, read-only calculators for the UK Construction Industry Scheme (CIS): deductions, gross up, tax months and deadlines, late filing penalties, the gross payment status turnover test, verification and nil returns. No key and no sign-in. Up to 60 requests a minute from one address. The same tools are served over MCP at https://0sand1s.co.uk/mcp. Answers are worked out from the rules as published; they are not tax advice and do not come from HMRC.'
  contact:
    url: https://0sand1s.co.uk/developers
servers:
- url: https://0sand1s.co.uk
tags:


# --- truncated at 32 KB (37 KB total) ---
# Full source: https://artifacts.apis.io/0sand1s-co-uk/openapi/0sand1s-co-uk-cis-api-openapi.yml