# `UsEin`

A US Employer Identification Number, for a business: nine digits.

Use it to name a US business with the IRS. For a person, use [`UsSsn`](/docs/types/type-us-ssn.md).

## Shape

One value, held as text in one set form, with no parts: `987654321`.

## Example

```jadpo
UsEin("123456789")
```

`UsEin(raw)` checks the text, and text that isn't one breaks the `format` rule.

`text.parse(raw, as: UsEin)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `12-3456789`, `12345678` or `1234567890`.

## Good to know

- Write it with no dash. `text.format` adds it: `12-3456789`.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.

## In JSON

A string, in a request, a response or `json.write`:

```json
"123456789"
"987654321"
```

## Details

<details>
<summary>Text form, storage, how it is shown, and operations</summary>

`UsEin` is in the group Tax and identity numbers, and has been in Jadpo since 0.1.0.

### Text form

`text.from` writes one standard text form, the same form `text.parse` reads back: `123456789` and `987654321`.

### How it is stored

It is stored in one column named for the field, of type `text`. `987654321` is stored as `'987654321'`.

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `123456789` | `12-3456789` |
| `987654321` | `98-7654321` |

### Operations

It also takes `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. [How every standard type behaves](/docs/every-standard-type-meets-one-contract.md) says how they work.

</details>