when i change Price Display Setting in configuration->Tax including and excluding Tax both in Display Product Prices In Catalog & Display Shipping Prices. following warning appears

Warning tax configuration can result in rounding errors . Please see source for more details.Click here to go to Tax configuration and change your settings.

i try my level best but not sure why is this, and its effect on tax and calculations


2 Answers 2


To solve, choose a taxation combination that doesn't generate the warning.

Magento has had a longstanding issue with rounding errors, especially when tax is involved, sometimes when discount rules are applied. They did a major rewrite of the code in 1.8 and 1.9 and added warning messages when certain combinations are used. You can use the setting, but it will cause rounding issues.

Rounding errors will cause differences between the sales order total pricing and what gets submitted on the credit card payment gateway. They also cause Paypal to decline accepting an order for payment if such a difference occurs.

Other answers where this has been discussed:

Tax rounding and catalog price rules

What is the status of rounding issues in 1.7?

Issue in tax configuration after Magento upgrade


Here is how is commented te part of the code which triggers the notice:

 * Check if tax calculation type and price display settings are compatible
 * invalid settings if
 *      Tax Calculation Method Based On 'Total' or 'Row'
 *      and at least one Price Display Settings has 'Including and Excluding Tax' value

file: app/code/core/Mage/Tax/Model/Config.php

Hope this helps

  • Do not hack your way in core files! Commented Mar 5, 2019 at 16:48

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