Sources Policy

Last updated: July 2026

1. Purpose of This Policy

This page defines the standards AKCalc applies when identifying, selecting, and citing sources for its calculators. It answers two questions that every user of a financial calculator should be able to ask:

• Where does this result come from?
• How do I verify it myself?

The Sources Policy operates alongside the Methodology page (which explains the research process) and the Editorial Policy (which covers publication standards). This page is specifically about the standard used to select sources — not how they are used once found.

The core rule that governs everything on this page:

2. What Qualifies as a Primary Source

A primary source, for the purposes of AKCalc, is a document that meets all three of the following criteria:

1. Published directly by the regulatory authority legally responsible for the rule, rate, or entitlement being calculated — not by a third party summarizing or interpreting that authority's rules.
2. Contains the actual formula, rate schedule, bracket table, or entitlement rule used in the calculation — not a general description of how the system works.
3. Is publicly accessible — so any user can open the document and verify the basis for the result independently.

A source that meets criteria 1 and 2 but is not publicly accessible (for example, a fee-gated legislative database) can still be used as the calculation basis, provided the citation on the calculator page identifies the document by name, issuing authority, and publication date clearly enough that a user or professional can locate it independently.

3. Primary Sources by Jurisdiction

The regulatory authority and the nature of the primary source differ by country. The following describes the sources used for each jurisdiction AKCalc currently covers:

United States — Federal

The federal tax authority is the Internal Revenue Service (IRS). Primary sources for US federal calculations include:

• IRS Publications (e.g., Publication 15-T Federal Income Tax Withholding Methods, Publication 15 Employer's Tax Guide, Publication 519 U.S. Tax Guide for Aliens, Publication 54 Tax Guide for U.S. Citizens and Resident Aliens Abroad)
• IRS Instructions for specific forms (e.g., Form W-4 instructions, Form 1116 instructions, Form 2555 instructions)
• IRS Revenue Procedures and Notices announcing annually adjusted thresholds and indexed amounts
• U.S. Code (USC) and Code of Federal Regulations (CFR) for legislative and regulatory provisions
• Official tax treaty text as published by the U.S. Treasury for cross-border and expat calculations

United States — State Level

Each state has its own tax authority. Primary sources for US state-level calculations include:

• California: California Franchise Tax Board (FTB) publications, Form DE 4 instructions, California SDI rate announcements from the California Employment Development Department (EDD)
• New York: New York State Department of Taxation and Finance publications and withholding tables, NYC Department of Finance guidance for local tax
• Texas: Texas Comptroller of Public Accounts guidance (Texas has no state income tax; sources cover applicable payroll rules)
• Ohio: Ohio Department of Taxation publications and municipal tax authority guidance from the Regional Income Tax Agency (RITA) and Central Collection Agency (CCA)
• Massachusetts: Massachusetts Department of Revenue (DOR) publications and withholding guides
• Georgia: Georgia Department of Revenue (DOR) withholding guides and IT-series form instructions
• Pennsylvania: Pennsylvania Department of Revenue publications and local earned income tax authority guidance
• All other states: The official state tax authority (department of revenue, department of taxation, or equivalent) is identified and its publications used

Germany

The primary tax authority is the Bundesministerium der Finanzen (BMF) — Federal Ministry of Finance. Primary sources include:

• Lohnsteuer Programmablaufplan (PAP) — the official published algorithm specifying the exact computation of Lohnsteuer withholding, released annually by BMF
• BMF-Schreiben (official ministerial letters) announcing rate changes, thresholds, and application guidance
• Einkommensteuergesetz (EStG) — Income Tax Act, as published on gesetze-im-internet.de (the official federal legislative database)
• Solidaritätszuschlaggesetz for the Solidaritätszuschlag (solidarity surcharge) rules
• Deutsche Rentenversicherung publications for pension insurance contribution rates and ceilings
• GKV-Spitzenverband announcements for statutory health insurance contribution rates
• Bundesagentur für Arbeit publications for unemployment insurance rates

Romania

The primary tax authority is ANAF (Agenția Națională de Administrare Fiscală) — the National Agency for Fiscal Administration. Primary sources include:

• Codul Fiscal (Tax Code) — as published in the Monitorul Oficial al României (Official Gazette), which is the legally authoritative text
• ANAF guidance and circulars interpreting specific provisions of the Tax Code
• Ordonanțe de Urgență (OUG) — government emergency ordinances published in the Monitorul Oficial that amend the Tax Code
• ANCPI tariff schedules for notarial and land registry fee calculators

Poland

The primary authority is the Ministerstwo Finansów (Ministry of Finance) for tax and ZUS (Zakład Ubezpieczeń Społecznych) for social insurance. Primary sources include:

• Ustawa o podatku dochodowym od osób fizycznych (Personal Income Tax Act — PIT Act) as published in the Dziennik Ustaw (Journal of Laws)
• ZUS official rate tables and announcements for social insurance contribution rates and annual earnings ceilings
• Ministerstwo Finansów interpretations and publications for application of PIT provisions

Gulf States (UAE, Saudi Arabia, Kuwait, Qatar, Oman, Bahrain)

End-of-service gratuity calculations are governed by each country's Labour Law. Primary sources are:

• UAE: Federal Labour Law No. 33 of 2021 (as amended) and MOHRE (Ministry of Human Resources and Emiratisation) guidance
• Saudi Arabia: Saudi Labour Law (Royal Decree M/51) and HRSD (Ministry of Human Resources and Social Development) publications
• Kuwait: Kuwait Labour Law No. 6 of 2010 (private sector) and Civil Service Law for public sector
• Qatar: Qatar Labour Law No. 14 of 2004 (as amended) and ADLSA guidance
• Oman: Oman Labour Law (Royal Decree 35/2003 as amended) and MLEI publications
• Bahrain: Bahrain Labour Law for the Private Sector (Law No. 36 of 2012) and MLSD guidance

All Other Countries

For any country not listed above, the same standard applies. Before a calculator is built, the primary regulatory authority for that jurisdiction is identified — the national tax administration, ministry of finance, social insurance institution, or relevant legislative body — and only documents published directly by that authority are used as formula sources. The specific authority and source document are named on the individual calculator page.

4. What Does Not Qualify as a Primary Source

The following are explicitly excluded as formula sources, regardless of how authoritative or well-known they may appear:

• Third-party financial websites — including major personal finance sites, payroll service providers, and financial news outlets. These sites may correctly summarize the rules, but they are not the source of the rules.
• Accounting firm and law firm articles — professional summaries, client bulletins, and explainer articles published by tax advisors or legal firms. These are secondary interpretations of the primary law.
• News articles and media reporting — even when reporting on official government announcements. The announcement itself is the primary source; the news article is not.
• Other online calculators — another calculator's output cannot verify our calculator's output. We only accept verification against the official formula document.
• AI-generated content — AI summaries and explanations of tax rules are never used as the basis for any formula, regardless of their apparent accuracy.
• Wikipedia and similar reference sites — useful for orientation, not for formula derivation.
• Forum and community posts — including Reddit, Stack Exchange, and professional association forums. These are used only to identify what to look for, not as a source of the rule itself.

Non-primary sources may be consulted during the research process to understand the landscape of a topic or to identify which official document to look for. However, the formula is always traced back to and implemented from an official primary document before publication.

5. Source Citation Standard on Calculator Pages

Every published calculator page displays a source block that identifies the specific document behind its result. This block contains:

• Document name — the full title of the specific publication or legislative text used (e.g., "IRS Publication 15-T, Federal Income Tax Withholding Methods")
• Issuing authority — the name of the government body that published it (e.g., "Internal Revenue Service")
• Publication date or applicable tax year — identifying which edition or version of the document was used (e.g., "Tax Year 2026")
• Last-verified date — the date a human reviewer most recently confirmed the calculator's implementation matches the current official publication. This is not the page modification date. See the Methodology page for the precise definition.
• Link to the official source — a direct link to the source document or the issuing authority's official website, where the document is publicly accessible

The purpose of this standard is verifiability. A user who questions any result should be able to open the cited document, locate the relevant section, and confirm independently that the formula used is correct.

6. When a Source Becomes Outdated

Tax rates, contribution thresholds, and entitlement rules change. A source document that was correct at the time of publication may become partially outdated when new legislation or a new rate schedule takes effect.

AKCalc addresses this through the monitoring and update process described in the Editorial Policy. In summary:

• Calculators are updated against the newly effective official source before rate changes take effect — not after the fact
• No calculator is updated based on a secondary source reporting a change. The update is made only once the new primary document is published and verified
• The last-verified date on the calculator page is updated to reflect the completed check against the new source

If you believe a source cited on any calculator page has been superseded by a newer official publication, please report it via the Contact page or by emailing [email protected]. Include the calculator URL and the specific new source you believe applies. Reports are reviewed within 48 hours.