Step 4 of 4 · BuildPick a gap, build it

15 activities with no open project. Pick one and build it.

Every gap below comes straight from the map: an activity of a company's tax department or a tax authority that has no open code yet. Each runs on published rules or a standard schema. That makes them the most buildable things in tax. Each gap says what to build on, what a first version could do, and which track on Learn helps.

  1. Build for a gap
  2. Write an agent skill
  3. Submit a project we missed
  4. Teach one lesson

The gaps, team by team

Company tax department

Direct & International Tax

International tax

Treaty rates, relief-at-source rules and reclaim procedures are public. No open dataset or logic yet.

Build on
The OECD Model Tax Convention and the treaty texts each country publishes.
A first version
A lookup that returns the treaty withholding rate on dividends, interest or royalties between two countries, citing the article it used.
See it on the map
Direct & International Tax

Pillar Two / global minimum tax

Published rules and a standard GIR schema. The most buildable gap on the site.

Build on
The OECD GloBE Model Rules, their Commentary and Administrative Guidance, and the GloBE Information Return with its XML schema.
A first version
Compute the effective tax rate and top-up tax for one jurisdiction from a handful of inputs, with tests built from the examples in the Commentary.
See it on the map
Tax Accounting & Reporting

Tax accounting & financial reporting

Templates, review and evidence, all specifiable. The core of every tax department, with nothing open.

Build on
The IAS 12 and ASC 740 standards, and a company's own trial balance and return data.
A first version
A deferred-tax roll-forward: temporary differences in, deferred tax and the rate reconciliation out, from a spreadsheet export.
See it on the map
Tax Accounting & Reporting

Tax forecasting & cash tax

A model over provision and payment data. Depends on the provision gap being filled first.

Build on
Statutory rates and instalment rules, and the output of a tax provision.
A first version
A cash-tax forecast for one country: forecast profit in, instalment payments and their due dates out.
See it on the map
Tax Accounting & Reporting

Transparency & external reporting

GRI 207 and the public CbCR templates are published standards. A reporting pack generator is a weekend project waiting for a fiscalist.

Build on
GRI 207, the OECD's country-by-country report and its XML schema, and the EU's public CbCR directive (2021/2101).
A first version
Turn entity-level data into the GRI 207-4 table and the EU public CbCR table, with totals reconciled to the accounts.
See it on the map
Transfer Pricing

Transfer pricing

Margin monitoring against an approved policy is a reconciliation problem with public inputs. Zero open implementations.

Build on
The OECD Transfer Pricing Guidelines, including the master file and local file contents in their annexes, and the group's own accounts.
A first version
Margin monitoring: each entity's operating margin against the policy's target range, and the year-end adjustment it needs.
See it on the map
Indirect Tax / VAT / GST

Customs & trade tax

Tariff schedules are public data. Classification assistants are an obvious agent-skill candidate.

Build on
National tariff schedules such as the EU's TARIC and the US Harmonized Tariff Schedule, and published binding tariff decisions.
A first version
An agent skill that proposes a tariff code for a product description, cites the heading and notes it used, and hands off to a person.
See it on the map
Controversy & Tax Risk

Tax risk management

A register with owners, scores and escalation thresholds. A schema and a workflow.

Build on
GRI 207-2 on tax governance, control and risk management, and the tax strategies that large groups publish.
A first version
A tax-risk register as an open schema and a small app: risk, owner, likelihood, impact, appetite, escalation threshold and next review.
See it on the map
Controversy & Tax Risk

Tax controls & assurance

The layer every auditor asks about. Controls, owners, evidence and test results: fully specifiable, zero open implementations.

Build on
The OECD's 2016 report on building better tax control frameworks, GRI 207-2, and the frameworks companies describe in their tax reports.
A first version
A control library as data: each control with its risk, owner, frequency, evidence and test steps, and a log of test results.
See it on the map
M&A / Transactions / Planning

Tax planning & business advisory

The rules-as-code frameworks on the list could power it. No open tool compares corporate structures yet.

Build on
Statutory corporate and withholding rates, treaty texts, and the rules-as-code frameworks already on the list.
A first version
Compare the tax cost of two or three group structures for one payment (a dividend, interest or a royalty), with every assumption shown.
See it on the map
M&A / Transactions / Planning

M&A, divestments & restructuring

Data-room reading is solved by generic document AI. Deal modelling and SPA clause libraries are not.

Build on
Merger agreements filed as public exhibits with securities regulators, and the statutory rules on losses and changes of ownership.
A first version
A library of SPA tax clauses from public merger agreements, tagged by type, that an agent can search and cite.
See it on the map

Tax authority

Returns, Payments & Debt

Returns processing & assessment

The validation rules sit in the law and the published return schemas. No open processing engine is in the list.

Build on
The return schemas and validation rules that tax authorities publish for filing software, and the law as code in OpenFisca or Catala.
A first version
A service that checks a filed return against its schema and its arithmetic and cross-field rules, and explains each rejection.
See it on the map
Returns, Payments & Debt

Payments, refunds & debt collection

Taxpayer accounting is a ledger with published rules. No open implementation is in the list.

Build on
The published rules on due dates, late-payment interest, penalties, refunds and payment plans.
A first version
A taxpayer account: charges, payments, interest and refunds by period, with the balance explained line by line.
See it on the map
E-invoicing & Real-time Reporting

Clearance & real-time reporting platforms

Open clients exist for the national platforms of many countries (see Indirect Tax on the company side). The receiving platforms themselves have no open implementation in the list.

Build on
EN 16931, Peppol BIS Billing 3.0 and their validation rules, and the national e-invoicing specifications tax authorities publish.
A first version
A reference receiving service: accept an e-invoice, validate it against EN 16931 and one national extension, store it and return an acknowledgement.
See it on the map
International Cooperation

Exchange of information & MAP

The exchange schemas are published by the OECD and the EU. No open tool is in the list.

Build on
The OECD's CRS and CbC XML schemas with their user guides, and the EU's DAC schemas.
A first version
A validator that checks a CRS or CbC file against the OECD schema and user guide, and lists every error in plain words.
See it on the map
Add to the list

Building one? Or know one we missed?

Every project on the list is open and used in tax work. Tell us about yours, or one you know. We review it before it goes on the list and the map.

Maintain something that belongs here?

Know one of these subjects from the inside? Teach one lesson.

Back to step 1ProjectsOpen tax projects for companies and tax authorities, in one list you can search by tax, country and kind.