Taxes and benefits can be calculated for different entities: persons, household, companies, etc.
The person entity within OpenFisca is unique and there is only one entity of this type. Some OpenFisca variables are defined for a person.
Example: a “salary” or someone’s age is defined for a person.
Group entities are clusters of persons such as a family, a household or a company. A tax and benefit system will likely define several entities and specify for each variable if it applies to a specific group entity or a person.
In France the legislation has these group entities:
"familles", (families)
"foyers_fiscaux" (tax units) and
"menages" (households).
In France for example, "taxe_habitation" (local tax) is calculated specifically for "menages".
Each person related to a group entity has a role inside this entity.
By way of example, within the OpenFisca France model the roles are:
for ‘familles’: parents and enfants (children),
for ‘foyers_fiscaux’: declarants (registrants) and personnes_a_charge (dependants),
for ‘menages’: personne_de_reference (reference person), conjoint, enfants and autres (other).
and within the OpenFisca Aotearoa Model the roles are:
for ‘families’: principal, partner, parent, child and other,
for ‘tenancies’: principal, tenant and other,
for ‘ownerships’: principal, owner and other,
for ‘Titled Properties’: owner and other,
You can define as many entities and roles as you want.
Entities and roles are described per the country, jurisdiction or domain, independent from the core engine (OpenFisca-Core). They can be identified in the texts of the modelled rules.