# `TaxRate`

A rate of tax, a percentage never below 0%: `20%`.

[Money and banking](types.md#money-and-banking); ordered; since Jadpo 0.1.0.

## Make one

It is a `Percentage` with bounds of its own: build one as you build a `Percentage`, and a value outside its bounds breaks `min` or `max`.

`text.parse(raw, as: TaxRate)` reads one from its text; text that isn't one at all fails `malformed`, such as `20`, `0.2` or `twenty percent`.

## Text, JSON and storage

`text.from` writes its canonical text, the one form `text.parse` reads back. JSON sends its canonical text as a string.

| Text | JSON |
|---|---|
| `0%` | `"0%"` |
| `5%` | `"5%"` |
| `20%` | `"20%"` |

It is stored in one column named for the field, of type `numeric`. `5%` is stored as `0.05`.

## Shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `0%` | `0%` |
| `5%` | `5%` |
| `20%` | `20%` |

## Operations

It has the contract's own operations: `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. It is ordered, so `<` and sorting take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.