> For the complete documentation index, see [llms.txt](https://helpwith.salesorder.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://helpwith.salesorder.com/accounting/tax/sales-tax/us-tax-codes.md).
# US Tax Codes
Tax Codes represent names and associated rates of Tax set by specific Tax Authorities. For this reason, Tax Codes are associated with their related Tax Authority via a drop-down list.
There are a few things worth noting:
* The Tax Authority drop-down is mandatory. Each code must be associated with a specific Tax Authority.
* The field 'Only used in Tax Group' requires a bit of explanation. Normally Tax Codes can be assigned directly to Sales Documents, such as Invoices. In some cases, it may be necessary to group Tax Codes together in a Tax Group and apply the collective rate. If this Tax Code is to be used exclusively in a Tax Group i.e. it is never applied in isolation, then ticking this box will remove it from the list of selectable Tax Codes on the Sales Documents. It is simply a method of reducing the number of selectable Tax Codes/Groups.
* The current and historical Tax Rates are entered into the table. If there are no entries the Tax Rate is set to zero.
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