Choose the full context.
Country, subdivision, industry, product, event, place basis, person, and tax year are explicit fields. The date of the event is recorded separately.
RIGHT CONTEXT. EXPLICIT EVIDENCE.
Know which rule
your answer used.
A useful calculation belongs to a place, a time, and a situation. We’re building those facts into the rule itself, so an answer can explain where it came from.
ILLUSTRATIVE RULE PACKv1.0.0
ScopePlace + activity + person
TimeEffective date + review due
EvidenceSource + tests + reviewer
One explicit version per result
Coverage status: architecture preview
The registry currently contains four fictional demonstration packs and zero real-world tax or regulatory packs. Existing tax tools use the rate you enter. No country’s tax, payroll, or legal rules are automatically selected.
01 / EXPLORE THE CONTRACT
DEMONSTRATION ONLYThe context comes first.
Change a field and see whether a rule can still be applied. Every fixture below is fictional.
A subdivision needs its own matching scope.
Product, person, place, and timing
These are independent facts. A language, currency, or industry name cannot fill them in reliably.
The review-check date is editable only to demonstrate expiry. A production approval gate must use a trusted server clock.
The event date selects the effective rule. The review-check date tests whether its evidence is still current. These are different questions.
Inspect the sources, review, and exclusions
EFFECTIVE PERIOD
2026-01-01 → 2027-01-01
Start included. End excluded.
REVIEW2026-10-29
Next review due: 2027-01-01
UseCalculator synthetic-fixture test suite
SOURCE EVIDENCE
UseCalculator fictional handling-fee specification
Retrieved 2026-10-29 · Fictional fixture specification v1
sha256:545a1895ae60cc9875ba172d3dc16156586fd79824d3f36baeea4786084b9fb2Assumptions
- The country and regional names are fictional.
- The entered amount is a nonnegative amount in demonstration units.
- The fee is a simple percentage of the entered amount, rounded once to two decimals.
Excluded from this example
- No real taxes, payroll, shipping prices, laws, or industry regulations are represented.
- No exemptions, thresholds, compounding, caps, or transaction-specific eligibility are modeled.
- A country-level fixture cannot be applied to a subdivision unless that exact scope has its own reviewed fixture.
03 / YOUR OWN ASSUMPTION
Already know the rate?
Use a percentage you supply. This worksheet does not select, approve, or verify a tax rate for you. Its result is always labeled as your own assumption.
Open the full user-entered tax toolDot decimals · two places for amount · up to four for rate
- Added amount
- 2.50
- Total after adding
- 102.50
A CONTRACT WE CAN CHECK
Six promises in the data model.
These constraints are enforced by the prototype resolver and tested against deliberate failures. They do not certify the correctness of a real legal interpretation.
Keep time in the model.
Every rule has an effective interval and a review interval. Event dates select the applicable version; a current review gate checks whether it may be used.
Keep the evidence attached.
Source URLs, exact source locations, retrieval dates, content fingerprints, assumptions, exclusions, and test evidence travel with each rule pack.
Stop when coverage is unclear.
Missing context, overlapping versions, unreviewed drafts, retired rules, and overdue reviews block automatic resolution. No silent national or industry fallback.
Run a constrained calculation.
A reviewed pack selects a known deterministic engine and bounded parameters. A downloaded rule cannot introduce executable JavaScript.
Preserve the original answer.
An exported run records its inputs, result, exact rule version, context, and review-check date. New rules do not rewrite a historical snapshot.
BEFORE A REAL RULE GOES LIVE
Evidence. Review. Then release.
Real coverage needs a country-by-country and domain-by-domain release process. A source URL and a passing test are necessary pieces of evidence; specialist interpretation and maintained ownership still matter.
- 01Document the exact question.
Include who and what the rule applies to, which place determines it, applicable dates, exemptions, thresholds, and excluded situations.
- 02Review primary authority.
Capture the official source, its exact section, effective dates, a content fingerprint, and a responsible reviewer.
- 03Test boundaries independently.
Check thresholds, rounding, periods, exemptions, and contradictory or missing inputs against approved expected answers.
- 04Release a fixed version.
Approve and publish an immutable pack. Assign a review deadline and invalidate affected coverage when source changes cannot yet be resolved.
Read the fictional fixture specification and fingerprints
The text below describes testing data created for this product. It is not a source of tax law, regulations, or commercial rates.
Fixture specification
UseCalculator synthetic handling-fee fixture specification v1. Country ZZ is fictional. ZZ national retail ordinary-goods sale delivery-location business has 200 basis points. ZZ-A retail ordinary-goods sale delivery-location business has 250 basis points. ZZ-A services professional-service sale delivery-location business has 400 basis points. ZZ-B retail ordinary-goods sale delivery-location business has 300 basis points and remains draft. All tax years are not applicable. Effective interval: 2026-01-01 inclusive to 2027-01-01 exclusive. These are test fixtures, not laws, taxes, prices, or recommendations.
sha256:545a1895ae60cc9875ba172d3dc16156586fd79824d3f36baeea4786084b9fb2Expected-answer evidence
Synthetic fixture expected answers v1: amount 100.00 at 2.00 percent gives added amount 2.00 and total 102.00; amount 100.00 at 2.50 percent gives 2.50 and 102.50; amount 100.00 at 4.00 percent gives 4.00 and 104.00; draft ZZ-B must not resolve; half-up 0.01 at 50 percent gives 0.01. Source, scope, date, ambiguity, and review gates are independently tested.
sha256:55adf786972f1a953d93f5afb42cc102d6a746cc1efed42cc17e13f71dae939dEach SHA-256 value fingerprints the exact corresponding text shown above. A fingerprint detects content changes; it does not establish legal authority or authenticate a reviewer.
The downloadable structure uses JSON Schema 2020-12. Runtime checks additionally enforce real dates, effective intervals, exact scope matching, and review status. The rule language currently implements only a bounded percentage engine.