> ## Documentation Index
> Fetch the complete documentation index at: https://gobl-improv.mintlify.site/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                                                  | Req. | Description                                                                                                                                                                 |
| ---------- | ----------- | ----------------------------------------------------- | ---- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Category   | `cat`       | [cbc.Code](/draft-0/cbc/code)                         | true | 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.                                                                                             |
| Rate       | `rate`      | [cbc.Key](/draft-0/cbc/key)                           |      | Rate within a category to apply.                                                                                                                                            |
| Percent    | `percent`   | [num.Percentage](/draft-0/num/percentage)             |      | Percent defines the percentage set manually or determined from the rate key (calculated if rate present). A nil percent implies that this tax combo is **exempt** from tax. |
| Surcharge  | `surcharge` | [num.Percentage](/draft-0/num/percentage)             |      | Some countries require an additional surcharge (calculated if rate 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.                                                                             |