Tax calculation methods

Tax calculation method options include Unit Price, Row Total, and Total. The following table explains how rounding (to two digits) is handled for different settings.

SettingCalculation and Display
Unit PriceCommerce calculates the tax for each item and displays prices tax-inclusive. To calculate the tax total, it rounds the tax for each item, and then adds them together.
Row TotalCommerce calculates the tax for each line. To calculate the tax total, it rounds the tax for each line item and then adds them together.
TotalCommerce calculates the tax for each item and adds those tax values to calculate the total unrounded tax amount for the order. It then applies the specified rounding mode to the total tax to determine the total tax for the order.

Catalog prices with or without tax

The possible display fields vary depending on the calculation method and whether the catalog prices include or exclude taxes. Display fields have two-decimal precision in normal computations. Some combinations of price settings display prices that both include and exclude tax. When both appear on the same line item, it can be confusing to customers, and triggers a warning.

SettingCalculation and Display
Excluding TaxUsing this setting, the base item price is used as it is entered and the tax calculation methods are applied.
IncludingTaxUsing this setting, the base item price that excludes tax is calculated first. This value is used as the base price, and the tax calculation methods are applied.
IMPORTANT
There are changes from earlier versions for EU merchants or other VAT merchants who display prices including tax and operate in several countries with multiple store views. If you load prices with more than two digits of precision, Commerce automatically rounds all prices to two digits to ensure that a consistent price is presented to buyers.

Shipping prices with or without tax

SettingDisplayCalculation
Excluding TaxAppears without tax.Normal calculation. Shipping is added to cart total, typically displayed as a separate item.
Including TaxCan be tax inclusive, or tax can be displayed separately.Shipping is treated as another item in cart with taxes, using the same calculations.

Tax amounts as line items

To display two different tax amounts as separate line items, such as GST and PST for Canadian stores, you must set different priorities for the related tax rules. However, in previous tax calculations, taxes with different priorities would automatically be compounded. To correctly display separate tax amounts without an incorrect compounding of the tax amounts, you can set different priorities, and also select the Calculate off subtotal only checkbox. This setting produces correctly calculated tax amounts that appear as separate line items.

Warning messages

Some combinations of tax-related options might be confusing to customers and trigger a warning. These conditions might occur when the tax calculation method is set to Row or Total, and the customer is presented with prices that both exclude and include tax. It can also occur when there is tax on a per-item basis in the cart. Because the tax calculation is rounded, the amount that appears in the cart might differ from the amount that a customer expects to pay.

If your tax calculation is based on a problematic configuration, the following warnings appear:

Exclamation point Warning. Tax discount configuration might result in different discounts than a customer might expect for store(s); Europe Website (French), Europe Website (German). Please see source for more details.

Exclamation point Warning. Tax configuration can result in rounding errors for store(s): Europe Websites (French), Europe Websites (German).