Step 2 of 4 · ProjectsBy jurisdiction

All projects By jurisdiction United Kingdom

81 open source tax projects for United Kingdom.

Every project on the list for United Kingdom, grouped by kind. Global tools have a page of their own. Entries without a warning come first in each group; the labels mark what to check.

81 projects68 maintained55 on the map22 jurisdictions + globalFacts checked 6 Oct 2026

Browse these by tax area

Income tax Corporate tax Benefits Payroll tax VAT & indirect Cross-cutting

Tax engines

6 projects

Rules-as-code that compute liabilities, returns and reforms.

PolicyEngineOpen tax-benefit models with a public app for scoring policy reforms.Tax engineUS · UK

PolicyEngine UKOpen-source static tax-benefit microsimulation model for the UK.Tax engineUK

UK land value taxDashboard that models replacing UK council tax with a land value tax.Tax engineUKLicence unknown

UK VATLabToolkit for modelling UK VAT policy.Tax engineUKLicence unknown

HMRC CT calculationsScala library for UK Corporation Tax return boxes and CT600 computations, including CT600A and CT600J.Tax engineUKArchived

taxpro-ukUK FRS 102 corporate tax provision system: AI prepares, a deterministic engine calculates, people approve.Tax engineUKNeeds a paid service

Calculators

11 projects

Small tools that compute one tax for one country.

beancount-plugin-tax-ukBeancount plugin that computes UK capital gains with Section 104 pooling and exports Excel reports.CalculatorUKFor individual taxpayers

BittyTaxCommand-line tools that turn wallet and exchange records into UK cryptoasset tax reports.CalculatorUKFor individual taxpayers

Capital Gains CalculatorPython tool for UK capital gains tax on broker transaction histories using HMRC matching rules.CalculatorUKFor individual taxpayers

cgt-toolCommand-line tool for UK Capital Gains Tax on share sales that applies HMRC matching rules offline.CalculatorUKFor individual taxpayers

CoolTaxToolUK tax calculator with charts for take-home pay, salary sacrifice and pension contributions.CalculatorUKFor individual taxpayers

Taxing212Browser-based UK capital gains calculator for Trading 212 CSV exports with Section 104 pooling.CalculatorUKFor individual taxpayers

UK Investment Tax CalculatorBrowser-based UK capital gains and dividend tax calculator for Interactive Brokers exports.CalculatorUKFor individual taxpayers

Labour Income Tax CalculatorAngular calculator showing how income tax would change under proposed Labour party policies.CalculatorUKInactive since 2019For individual taxpayers

tax_compareFlask website for comparing income tax in different regions; the README names no region or year.CalculatorUK · DEInactive since 2022For individual taxpayers

Tax-Provision-Day-17-of-30UK corporation tax provision estimator: book-to-tax, marginal relief, IAS 12 and FRS 102 deferred tax.CalculatorUKDemo

UK Trade Tariff duty calculatorThe Online Trade Tariff's Rails duty calculator, archived in June 2025.CalculatorUKArchived

MCP

1 project

Open connectors and protocols between agents and legislation, case law and ledgers.

UK Trade Tariff MCP serverMCP server from the UK tariff team: commodity-code lookup on the Online Trade Tariff as tools for AI clients.MCPUK

APIs

44 projects

Validation, rates, filings and registries you can call directly.

ct600-filingCommand-line tool that files a CT600 corporation tax return with HMRC.APIUK

customs-domainPHP domain logic for commodity code validation, UK Trade Tariff mapping and compliance rules.APIUK

HMRC Advance Tariff Rulings serviceHMRC's Advance Tariff Rulings service: application frontend, case backend, rulings search, case manager.APIUK

HMRC Assist (Self Assessment)API that generates an HMRC Assist report of risk messages for a Self Assessment return before submission.APIUK

HMRC CDS FinancialsHMRC's CDS financial services: duty deferment statements, cash and guarantee accounts.APIUK

HMRC Country-by-country reportingHMRC's service for uploading country-by-country reports as XML files, with its backend and file validation.APIUK

HMRC CRS/FATCA reporting serviceHMRC's CRS and FATCA reporting service: registration, institution management and report upload.APIUK

HMRC Customs Declaration Service APIsHMRC's Customs Declaration Service APIs: submit, amend and cancel declarations, upload documents.APIUK

HMRC Customs Exports Declaration ServiceHMRC's Customs Exports Declaration Service: trader frontend, declaration backend and the movements service.APIUK

HMRC customs inventory linking APIsHMRC's inventory linking APIs for import declarations and for export consignment consolidation and movement.APIUK

HMRC Digital Platform Reporting serviceHMRC's Digital Platform Reporting service (DAC7 rules): registration, operators, seller-data XML filing.APIUK

HMRC Digital Services TaxHMRC's Digital Services Tax service: registration and returns, with a frontend and test stubs.APIUK

HMRC Enhanced Self Serve Time To PayHMRC's payment-plan journey for tax debts: eligibility check, affordability and plan selection, and backend.APIUK

HMRC EORI servicesHMRC's EORI services: an API that checks a GB EORI number and returns trader details, with its backend.APIUK

HMRC EU VAT refundsHMRC service for EU VAT refund claims, started in 2026.APIUK

HMRC financial transactions (VAT)Service returning MTD VAT liabilities, payments and late-payment penalty details, with direct debit checks.APIUK

HMRC Import Control System (ICS2)HMRC's import control services: entry summary declaration store, ICS2 WSDL schemas, safety and security guide.APIUK

HMRC Income Tax (MTD) servicesHMRC service that collects dividend, interest, Gift Aid, CIS, employment and pension data for Income Tax MTD.APIUK

HMRC individuals charges APIAPI to view and manage individuals' pension and high income child benefit charges.APIUK

HMRC Mandatory Disclosure Rules serviceHMRC's mandatory disclosure rules (MDR) service: credentials and subscription details, XML checks, submission.APIUK

HMRC New Computerised Transit System (NCTS)HMRC's transit services: traders API, NCTS validator and converter, movement store, documents, guarantees.APIUK

HMRC payments servicesHMRC's payment services: processor, orchestrator, card, mobile and telephone payments, national direct debit.APIUK

HMRC penalties serviceHMRC's late-submission and late-payment penalty service: backend, VAT and income tax frontends, appeals.APIUK

HMRC Pillar 2 servicesHMRC's Pillar Two service code: the submission API, the registration frontend and backend, and test stubs.APIUK

HMRC Self Assessment accounts APIAPI for a Self Assessment account: balance (overdue, payable, pending), charges, payments and allocations.APIUK

HMRC Self Assessment calculation APIsHMRC's MTD APIs that trigger and return a Self Assessment calculation, with the liability, BSAS and BISS APIs.APIUK

HMRC Self Assessment refundFrontend for claiming a Self Assessment refund.APIUK

HMRC Senior Accounting Officer serviceHMRC's Senior Accounting Officer service: registration, hub, notification and certificate submission.APIUK

HMRC submission trackerService that tracks the status of forms and submissions sent to HMRC.APIUK

HMRC third-party payments APIExternal API that lets third-party software initiate a payment to HMRC.APIUK

HMRC Time to PayHMRC's Time to Pay services: the arrangement backend, the self-service frontend, proxy API and taxpayer data.APIUK

HMRC VAT APIHMRC's Making Tax Digital VAT API: obligations, returns, payments, liabilities and penalties.APIUK

HMRC VAT repayment trackerService where businesses track the progress of a VAT repayment: frontend and backend.APIUK

HMRC View and change income tax (MTD)Frontend where MTD income tax customers view calculations, charges and payments and make changes.APIUK

hmrclibTyped Python clients for 73 HMRC APIs: Pillar 2 submission, customs declarations, Making Tax Digital and more.APIUK

hs-code-lookupJavaScript library that parses, validates and looks up HS codes with MFN duty rates for US, EU, UK and China.APIUS · EU · UK · CN

tax-idsRust crate that validates VAT and GST numbers in the EU, UK, Switzerland and Norway.APIEU · UK · CH · NO

tax-kalculatorKotlin Multiplatform library that works out UK take-home pay after tax, National Insurance, pension and loans.APIUK

UK Online Trade TariffThe UK Online Trade Tariff: API, website, admin tool and electronic tariff file for codes, duties and quotas.APIUK

valvatRuby gem that validates EU and UK VAT numbers, standalone or as an ActiveModel validator.APIEU · UK

VATValidationVAT number validator with GUI, CLI and REST API for German, EU, UK and Swiss checks.APIDE · EU · UK · CH

HMRC DAC6 disclosure serviceHMRC's DAC6 cross-border arrangement disclosure service, archived in March 2024 when the UK moved to MDR.APIUKArchived

m2-vatfallbackMagento 2 module that validates VAT numbers by API, with an offline regex fallback for VIES outages.APIEU · UKArchived

Stanza VAT Validator (C#).NET client for a hosted EU and UK VAT number validator and rate lookup.APIEU · UKNeeds a paid service

Automations

12 projects

Reusable workflows for provisions, reconciliations and compliance runs.

PolicyEngine ChatChat interface to PolicyEngine for UK and US tax and benefit questions and reforms.AutomationUS · UKLicence unknown

PolicyEngine UK ChatChat assistant for UK tax and benefit policy, powered by PolicyEngine.AutomationUKLicence unknown

TaMaTo (Tariff Management Tool)The Department for Business and Trade's Tariff Management Tool for UK import and export tariff data; a copy.AutomationUK

basic-python-tariff-queryPython library that parses Online Trade Tariff commodity URLs into their key objects; archived.AutomationUKArchivedLicence unknown

CbcXml (UK)C# tool that turns a fixed Excel template into UK country-by-country report XML and validates it.AutomationUKInactive since 2020Licence unknown

download-CDS-filesUtility from the UK tariff team for downloading Customs Declaration Service files; archived.AutomationUKArchivedLicence unknown

eori-validatorValidates EU and GB EORI numbers against the EU customs and HMRC registries, as a Next.js app.AutomationEU · UKNeeds a paid serviceLicence unknown

ott-agentSpike from the UK tariff team: a Bedrock and Claude chat with commodity monitoring over the tariff MCP server.AutomationUKDemoNeeds a paid serviceLicence unknown

preference-utilisation-analysisPython tools analysing the utilisation of trade preferences; archived.AutomationUKArchivedLicence unknown

rules-of-origin-builder-ukTranslates the UK's rules-of-origin reference documents into a usable data format; archived.AutomationUKArchivedLicence unknown

rules-of-origin-builder-xiScrapes rules-of-origin data for the Northern Ireland and EU tariff; archived.AutomationUK · EUArchivedLicence unknown

trade-tariff-classification-examplesProof-of-concept tariff classification implementations and examples from the UK tariff team; archived.AutomationUKArchivedDemoLicence unknown

Tax datasets

5 projects

Rates, treaties and statistics, open and versioned.

apparel-hs-codesOpen JSON database of apparel and textile HS codes with MFN duty rates for the US, EU, UK and Australia.Tax datasetUS · EU · UK · AU

hmrc-exchange-ratesJSON mirror of HMRC's monthly exchange rates for customs and VAT, 2015 to 2026, updated automatically.Tax datasetUKLicence unknown

myTransferPricing referenceSummaries of 18 OECD transfer pricing country profiles, with a prompt that reviews a Local File against one.Tax datasetAT · BE · BR · DK · FR · DE · GR · IE · IT · LU · NL · PL · SG · ES · SE · CH · UK · US

PolicyEngine UK dataBuilds calibrated UK household microdata for PolicyEngine, reweighted against national targets.Tax datasetUKLicence unknown

taric-opendataAutomated mirrors of tariff data from 18 sources (EU TARIC, GB, NO, CH, US) plus EBTI and ATaR rulings.Tax datasetEU · UK · NO · CH · US · Global

Benchmarks

1 project

Evals that show whether a model reasons about tax, or guesses.

UK Trade Tariff AI search evaluation suiteEvaluation suite for the UK tariff team's AI classification and search experiments on the Online Trade Tariff.BenchmarkUKDemo

Models

1 project

Open AI models trained or tuned for tax text.

UK Trade Tariff FPO commodity searchMachine-learning service from the UK tariff team that suggests commodity codes from parcel descriptions.ModelUK

Labels mark what to check before you rely on an entry: inactive or archived code, demos, paid services and unclear licences. Only maintained projects for companies and tax authorities appear on the map. Search and filter the whole list.

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Next · Step 3 of 4The gapsThe activities with no open project yet, and the partly covered ones, with what to build on.