Categories organize the line items used on Flute invoices.

Categories are intended to be a convenient way to group and locate line items.
Line items are used to create invoices.
Each line item is product or service with predefined values such a name, unit type, and price.
To build an invoice, add the appropriate line items to itemize billing.

Categories can organize groups of line items.
The use of categories is optional.

A category may contain zero, one or more line items.
Line items may be assigned to a category.
However, line items are not required to be assigned to a category.
For more about line items, see [Line Items](#line-items-overview).

Each category has:

* A name, which must be unique within a merchant account.
* An optional default unit type, such as each, hour, or pound, that applies automatically to line items created under it.


A category may be deleted,
This does not delete the line items assigned to it.
Those line items will remain but without a category.

Each category returned by the API also reports an item count.
This gives a quick view of how many line items currently belong to it.
With that information, a merchant may decide to rename, reassign, or delete it.

The Categories endpoints support listing, creating, updating, and removing categories.
The following endpoints are available:

| Endpoint | Explanation |
|  --- | --- |
| GET /pay-int-api/categories | The list endpoint accepts a search string along with paging and sort parameters. A merchant catalog with many categories can be filtered to relevant results rather than paged through in full. |
| POST /pay-int-api/categories | Creates a new category. The category name must be unique within the merchant account. |
| PUT /pay-int-api/categories/{categoryId} | Updates an existing category's name or default unit type. The name must remain unique within the merchant account. |
| DELETE /pay-int-api/categories/{categoryId} | Deletes a category. Line items that referenced it stay in the catalog, now with an empty category. |