Eligibility rules

A measure’s eligibility.rules is a list of rule nodes that must all hold. The matcher evaluates them against the facts of a match request; the full record serves them as they are, so you can show or evaluate them yourself. Topics are kept apart on purpose: a topic is a reason to show a measure, a rule is a condition to meet.

Nodes#

Nodes are told apart by their keys. The top-level list is an implicit all. A condition’s id is stable within its measure (region, size, applicant_type, nace, age_max), which is how the change feed can say which rule changed: eligibility.rules[age_max].

Here are the rules of the federal Tax Shelter for start-ups: the Belgian company code’s small-company test (at least two of three criteria) as an any of three pairs, then an age limit. Provenance is shortened in the first six.

[
  {
    "any": [
      {
        "all": [
          {
            "id": "size",
            "field": "company.employees",
            "op": "lte",
            "value": 50,
            "provenance": "…"
          },
          {
            "id": "size_turnover_a",
            "field": "company.turnover_eur",
            "op": "lte",
            "value": 11250000,
            "provenance": "…"
          }
        ]
      },
      {
        "all": [
          {
            "id": "size_employees_b",
            "field": "company.employees",
            "op": "lte",
            "value": 50,
            "provenance": "…"
          },
          {
            "id": "size_balance_b",
            "field": "company.balance_sheet_eur",
            "op": "lte",
            "value": 6000000,
            "provenance": "…"
          }
        ]
      },
      {
        "all": [
          {
            "id": "size_turnover_c",
            "field": "company.turnover_eur",
            "op": "lte",
            "value": 11250000,
            "provenance": "…"
          },
          {
            "id": "size_balance_c",
            "field": "company.balance_sheet_eur",
            "op": "lte",
            "value": 6000000,
            "provenance": "…"
          }
        ]
      }
    ]
  },
  {
    "id": "age_max",
    "field": "company.age_years",
    "op": "lt",
    "value": 4,
    "label": {
      "nl": "In de eerste vier jaar na de oprichting",
      "fr": "Dans les quatre premières années après la constitution",
      "en": "Within the first four years after incorporation",
      "de": null
    },
    "provenance": {
      "method": "curated",
      "source_url": "https://financien.belgium.be/nl/ondernemingen/tax-shelter-kleine-ondernemingen/startende-start-up",
      "source_section": null,
      "review_status": "verified",
      "reviewed_at": "2026-09-27",
      "note": "Completed years: the fifth year after incorporation belongs to the scale-up regime."
    }
  }
]

Three values#

A fact the caller did not give is unknown, never assumed, and so is a fact of a shape the operator cannot compare, or a rule whose value is malformed: a broken rule never passes by accident. The outcome of the whole tree is one of the three, and it decides the match status. The facts that were unknown where knowing them could change the outcome are reported as unknowns; once a tree is decided (a failure in an all, a pass in an any) its unknowns are dropped, because nothing is left to ask.

Fields#

A closed list: a rule over a fact the matcher cannot be given would be a rule that is always unknown. request_path is the match request property that supplies the fact, and what unknowns and missing_information point you to.

GET /v1/taxonomy returns the same list as rule_fields, each with the question to ask in Dutch, French and English.

Operators#

Strings compare case-insensitively. Numbers may be given as JSON numbers or numeric strings.

Labels#

A rule can bring its own label ({ nl, fr, en, de }), usually the words of the official page; the field is left out of the record when it has none. Otherwise a label is generated from the field, operator and value in each service language: Project cost at least €25,000, Projectkost minstens € 25.000, Coût du projet au moins 25 000 €. A match’s reasons carry the label in the language you asked for.

Provenance and review status#

Every condition carries where it came from:

Where rules come from

• From structured fields: a regional measure gets a region rule (contains_any on company.regions), a size restriction a size rule, a list of applicant types an applicant_type rule, sector lists nace and nace_excluded rules. Their review_status is auto.
• From patterns in the text (a maximum or minimum company age, for instance): method is text_pattern and review_status is unreviewed.
• Written from the official page: method is curated and review_status is verified. Such a rule replaces the automatic rule with the same id.

The measure’s rules_basis sums this up (none, derived, extracted, curated), and its confidence says how much of what decides eligibility the rules capture: 0.9 for curated rules unless set otherwise, 0.6 for extracted, 0.45 for derived. Only curated or extracted rules at 0.7 or more can make a match likely_eligible.