Taxley (UK Corporation Tax API)

Taxley provides free UK Corporation Tax calculators and a public JSON API for developers and AI assistants. It offers tools to compute corporation tax, deadlines, penalties, and related calculations without requiring an API key. Results link back to Taxley’s website for verification. The service is operated by Taxley UK LLP, a UK‑registered limited liability partnership, and integrates with HMRC filing processes.

Taxley (UK Corporation Tax API) publishes 2 API contracts indexed on the APIs.io network, including Tools API, and 1 more. Tagged areas include Company, Tax, United Kingdom, and Finance.

The Taxley (UK Corporation Tax API) catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

Taxley (UK Corporation Tax API)’s developer surface includes support, pricing, documentation, and 23 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

35.4/100 thin ▼ -7.3 Agent 33/100 agent ready Heartbeat 100/100 alive Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessPaid

1 published contract 1 MCP Servers

Company Tax United Kingdom Finance

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Tax Management

BC-220

Tools

GET /api/v1/tools GET /api/v1/tools/corporation-tax GET /api/v1/tools/deadlines GET /api/v1/tools/late-penalty

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 35.4/100 · thin

Contract Quality 10.4 / 19

Developer Ergonomics 1.1 / 15

Access Clarity 8.1 / 15

Operational Transparency 0.5 / 10

Contract Governance 2.0 / 9

Discoverability 4.4 / 8

Regulatory Posture 3.1 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 33/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented)
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)

8 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Developer Ergonomics scores 7.1 — up to +18.6 composite points
Operational Transparency scores 5.3 — up to +12.3 composite points
Contract Quality scores 55.5 — up to +11.1 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/taxley/apis.yml: open an issue on github.com/api-evangelist/taxley to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 2

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

Model Context Protocol (MCP)

measured — observed by APIs.io (documented)

OpenAPI

measured — observed by APIs.io (published)

APIs 2

Individual APIs this provider publishes, each with its own machine-readable definition.

Taxley API

Taxley provides free UK corporation tax calculators via a public JSON API.

Taxley (UK Corporation Tax API) Tools API

The Tools API from Taxley (UK Corporation Tax API) — 18 operation(s) for tools.

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

Taxley (UK Corporation Tax API) MCP Server

Remote MCP server at taxley.co.uk.

MCP SERVER

Taxley (UK Corporation Tax API) pricing

Prices published by Taxley (UK Corporation Tax API).

Plan	Price
Dormant company return	£9.50
Return with micro-entity accounts	£49.95
Return with small-company accounts	£139.00

Plan details, limits and sources →

Pricing Plans 1

Published pricing tiers and plan structures.

Taxley Plans Pricing

3 plans

PLANS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

Taxley (UK Corporation Tax API)

SLA

FinOps 1

Cost, billing, and metering signals for API financial operations.

Taxley Finops

FINOPS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Taxley Context

2 classes · 9 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Taxley (UK Corporation Tax API) API Rules

54 rules · 48 errors 5 warnings 1 info

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions for this provider's data models.

ToolRun

7 properties

JSON SCHEMA

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Taxley Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Taxley Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Taxley Agentic Access

35 operations · 17 acting

AGENTIC

Resources

Get Started 1

Portal, sign-up, and the first successful call

Login

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

LLMsTxt

MCPServer

WellKnown

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

DataModel

ErrorCatalog

Conformance

Access & Security 4

Authentication, authorization, and security posture

SecurityTxt

SecurityTxt

Security

Security

VulnerabilityDisclosure

VulnerabilityDisclosure

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 5

Pricing, plans, and the legal terms of use

FinOps

Plans

TermsOfService

PrivacyPolicy

Pricing

Company 2

The organization behind the API

Newsroom

Newsroom

Website

Website

Other 2

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Hosts

Hosts

Source (apis.yml)

aid: taxley
name: Taxley (UK Corporation Tax API)
accessModel:
  pricing: paid
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Paid
  confidence: low
  probe_state: unreadable
  source:
  - plans
  - security
  generated: '2026-11-06'
  method: derived
image: https://taxley.co.uk/images/og/taxley-share-v1.jpg
description: Taxley provides free UK Corporation Tax calculators and a public JSON API for developers and AI assistants. It
  offers tools to compute corporation tax, deadlines, penalties, and related calculations without requiring an API key. Results
  link back to Taxley’s website for verification. The service is operated by Taxley UK LLP, a UK‑registered limited liability
  partnership, and integrates with HMRC filing processes.
url: https://raw.githubusercontent.com/api-evangelist/taxley/refs/heads/main/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-15 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-15'
modified: '2026-10-15'
tags:
- Company
- Tax
- United Kingdom
- Finance
tags_raw:
- Company
- Tax
- UK
- Finance
- API
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: FinOps
  url: finops/taxley-finops.yml
- type: CapabilityMap
  url: capabilities/taxley-capability-edges.yml
  name: Taxley (UK Corporation Tax API) Business Capability Map
- type: AgenticAccess
  url: agentic-access/taxley-agentic-access.yml
- type: Plans
  url: plans/taxley-plans-pricing.yml
- type: Spectral
  url: rules/taxley-rules.yml
- type: JSONLD
  url: json-ld/taxley-context.jsonld
- type: Vocabulary
  url: vocabulary/taxley-vocabulary.yml
- type: DataModel
  url: data-model/taxley-data-model.yml
- type: ErrorCatalog
  url: errors/taxley-problem-types.yml
- type: Conformance
  url: conformance/taxley-conformance.yml
- type: LLMsTxt
  url: llms/taxley-llms.txt
- type: MCPServer
  url: mcp/taxley-mcp.yml
- type: SecurityTxt
  url: well-known/taxley-security.txt
- type: WellKnown
  url: well-known/taxley-well-known.yml
- type: Hosts
  url: hosts/taxley-hosts.yml
- type: TermsOfService
  url: https://taxley.co.uk/legal/terms
- type: Support
  url: https://taxley.co.uk/help
- type: Security
  url: https://taxley.co.uk/security
- type: PrivacyPolicy
  url: https://taxley.co.uk/legal/privacy
- type: Pricing
  url: https://taxley.co.uk/pricing
- type: Newsroom
  url: https://taxley.co.uk/press
- type: Login
  url: https://taxley.co.uk/login
- type: VulnerabilityDisclosure
  url: security/taxley-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/taxley-domain-security.yml
- type: Website
  url: https://taxley.co.uk
- type: Documentation
  url: https://taxley.co.uk/developers
apis:
- name: Taxley API
  description: Taxley provides free UK corporation tax calculators via a public JSON API.
  humanURL: https://taxley.co.uk/developers
  baseURL: null
  aid: taxley:taxley-api
- aid: taxley:taxley-tools-api
  name: Taxley (UK Corporation Tax API) Tools API
  description: The Tools API from Taxley (UK Corporation Tax API) — 18 operation(s) for tools.
  humanURL: https://taxley.co.uk/developers
  tags:
  - Tools
  properties:
  - type: OpenAPI
    url: openapi/taxley-tools-api-openapi.yml
  - type: JSONSchema
    url: json-schema/taxley-tool-run-schema.json
x-submission-notes: Free no-key UK corporation tax calculators
x-submission-probe: root 200, developers 200, /api/v1/openapi.json 200, soft-404 OK
x-coverage:
  state: unreadable
  reason: no-machine-readable-spec
  detail: The developers page returns HTML with no OpenAPI or other machine‑readable contract.
  evidence:
  - url: https://taxley.co.uk/developers
    status: 200
  checked: '2026-10-15'
x-submitted-by: alex@taxley.co.uk (apis.io/add, 2026-10-14)
x-enrichment:
  date: '2026-10-15'
  status: enriched
  artifacts_added: 24
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

Taxley (UK Corporation Tax API) — frequently asked questions

Does Taxley (UK Corporation Tax API) have an API?

Yes. APIs.io lists 2 APIs from Taxley (UK Corporation Tax API), including Taxley API and Taxley (UK Corporation Tax API) Tools API.

Is there an OpenAPI specification for the Taxley (UK Corporation Tax API)?

Yes. APIs.io indexes 1 OpenAPI specification for Taxley (UK Corporation Tax API), each linked for download from this page.

How much does the Taxley (UK Corporation Tax API) cost?

Taxley (UK Corporation Tax API) publishes its prices; its Dormant company return plan is £9.50 as of 2026-10-15. APIs.io lists 3 pricing plans for Taxley (UK Corporation Tax API), with each plan's price, limits and inclusions under Pricing on this page.

Does Taxley (UK Corporation Tax API) have an MCP server?

Yes. APIs.io lists 1 MCP server for Taxley (UK Corporation Tax API): Remote MCP server at taxley.co.uk.

Is the Taxley (UK Corporation Tax API) ready for AI agents?

Taxley (UK Corporation Tax API) has a Kin Score of 35.4 out of 100 (thin) and an Agent Readiness score of 33.3 (agent-ready), scored by API Evangelist on 2026-11-06.

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