# Jurisdictions and tax years [#jurisdictions-and-tax-years]

Jurisdiction and tax year are calculator context values. They are not separate
top-level route families.

## When this matters [#when-this-matters]

Pass context when you need a specific supported tax year or want metadata
filtered to a jurisdiction. Do not default tax-significant context in your
application unless the owning schema defines that default.

## How it works [#how-it-works]

```json
{
  "facts": {
    "taxableIncome": { "_tag": "Money", "cents": 9000000, "currency": "AUD" }
  },
  "jurisdiction": "AU",
  "taxYear": "2025-26"
}
```

The calculator package composes supported jurisdiction and tax-year literals
from rule packages. Unsupported combinations return a
`CalculatorServiceError`.

## Related concepts [#related-concepts]

* [Calculators](/concepts/calculators)
* [API endpoints](/api/endpoints)
* [API and SDK architecture](https://github.com/crcorbett/taxkit/blob/a151e51e8a30247526fa93412df046955846eca4/docs/architecture/api-and-sdk.md)