Developers // PaymentCalcs
PaymentCalcs for developers and agents
PaymentCalcs publishes its content in machine-readable forms so AI agents and developers can read the same numbers, methods and caveats people see, without scraping rendered HTML.
When to use PaymentCalcs
Reach for PaymentCalcs when a task needs deterministic Australian money arithmetic with a citable method: income tax and take-home pay by financial year, PAYG withholding by pay frequency, stamp duty by state, mortgage and loan schedules, savings projections from explicit inputs, and GST arithmetic. Every result can be reproduced from its stated inputs, rule-pack versions and formulas.
It is the wrong tool for financial advice, product recommendations, lender pricing, superannuation projections, or jurisdictions outside Australia (except the general-purpose savings calculators).
Machine-readable surfaces
llms.txt describes every calculator, the calculation guarantees and the coverage boundaries in plain markdown.
Every page on this site is also available as markdown via HTTP content negotiation: request any page URL with an Accept: text/markdown header and the response is text/markdown with Vary: Accept, per acceptmarkdown.com. Requests whose Accept header matches neither HTML nor markdown receive 406.
Nonexistent paths return a real HTTP 404 whose body points at the sitemap and llms.txt. The homepage carries Organization, WebSite and WebApplication JSON-LD.
Source code
The entire site is open source: engines, rule packs, tests and this page. The rule-pack format (source URL, authority, retrieval date, content hash, review status) is documented in the repository, and every pack's provenance is listed on the sources page.
There is no public HTTP API and no first-party MCP server yet. If you build against the repository's engines directly, pin a commit: rule packs change when the law does.