Tax services: Item fees in the tax provider response

Tax service providers can now return an optional fees array for each item in the response to Checkout. Use it for charges that aren't taxes, such as regulatory or commercial fees, so they're kept apart from the taxes applied to the order.

Until now, the tax provider response has only accepted a taxes array. Any charge returned by the provider was handled as a tax, even when it wasn't a fiscal or government charge. For example, a deposit for returnable packaging that varies by state had to be returned as a tax, which added it to the tax total and resulted in incorrect fiscal values.

The tax provider can now also return a fees array for each item, at the same level as taxes and with the same fields. When the provider returns fees, Checkout:

• Adds each fee to the item's priceTags with the FEE@{name} prefix. Taxes keep the TAXHUB@{name} prefix.
• Adds the fee values to a new Fee totalizer in the cart and order, separate from the CustomTax totalizer that adds up the taxes.

No action is required. The fees array is optional, and integrations that only return taxes work as before.

If your tax provider calculates charges that aren't taxes, you can return them in the fees array. For the full response format and examples, see Item fees in the Tax services specification guide.