> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gobl.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Combo

Combo represents the tax combination of a category code and rate key.

## Schema ID

`https://gobl.org/draft-0/tax/set#/$defs/Combo`

## Properties

| Title      | Property    | Type                                                  | Description                                                                                                                                        |
| ---------- | ----------- | ----------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
| Category   | `cat`       | [cbc.Code](/draft-0/cbc/code)                         | Tax category code from those available inside a region.                                                                                            |
| Country    | `country`   | [l10n.TaxCountryCode](/draft-0/l10n/tax_country_code) | Country code override when issuing with taxes applied from different countries.                                                                    |
|            | `key`       | [cbc.Key](/draft-0/cbc/key)                           | Key helps determine the tax situation within the category.                                                                                         |
| Rate       | `rate`      | [cbc.Key](/draft-0/cbc/key)                           | Rate within a category and for a given key to apply.                                                                                               |
| Percent    | `percent`   | [num.Percentage](/draft-0/num/percentage)             | Percent defines the percentage set manually or determined from the key. A nil percent implies that this tax combo is either exempt or not-subject. |
| Surcharge  | `surcharge` | [num.Percentage](/draft-0/num/percentage)             | Some countries require an additional surcharge (may be determined if key present).                                                                 |
| Extensions | `ext`       | [tax.Extensions](/draft-0/tax/extensions)             | Local codes that apply for a given rate or percentage that need to be identified and validated.                                                    |

## Validation Rules

| Field                | Test                                                           | Validation Code / Message                                                        |
| -------------------- | -------------------------------------------------------------- | -------------------------------------------------------------------------------- |
| <small>Combo</small> | <ul class="gobl-test"><li>Category in regime</li></ul>         | `GOBL-TAX-COMBO-01`<br />Tax category not valid for regime                       |
| <small>Combo</small> | <ul class="gobl-test"><li>Key in category</li></ul>            | `GOBL-TAX-COMBO-02`<br />Tax combo key not valid for category in regime          |
| <small>Combo</small> | <ul class="gobl-test"><li>Rate in key</li></ul>                | `GOBL-TAX-COMBO-03`<br />Tax combo rate not valid for key in regime              |
| <small>Combo</small> | <ul class="gobl-test"><li>Percent valid for key</li></ul>      | `GOBL-TAX-COMBO-04`<br />Tax combo percent required or invalid for key in regime |
| <small>Combo</small> | <ul class="gobl-test"><li>Surcharge requires percent</li></ul> | `GOBL-TAX-COMBO-05`<br />Tax combo surcharge requires percent in regime          |
| <small>Combo</small> | <ul class="gobl-test"><li>Extension keys defined</li></ul>     | `GOBL-TAX-COMBO-06`<br />Tax combo extension key not defined in regime           |