There could be several reasons why an incorrect sales tax is being calculated on an order, I'll detail some of the potential reasons below:
Product tax: Have all products been set to charge taxes? As seen in the image below, some products may have this option turned off, so no taxes would be calculated on them. You can check the Product page of the items that your customer ordered to double check whether or not the specific products have been set to charge taxes.
Requireshipping: When a product is set up as not requiring shipping, it is counted as a digital product and the billing address is used instead of the shipping address when calculating tax on these products. If you're using the Shopify Tax engine, a mixed order of digital and physical products will use the shipping address.
You can navigate to the Product page and scroll down to the Shipping section, as seen below, and ensure that Physical product has been selected so that the system recognizes that the product requires shipping.
Order imported from another platform: Was the order made directly on Shopify, or has it been imported to your account from another platform? Depending on the app or platform (e.g. Amazon, eBay etc.), they may do their own tax calculations and not rely on Shopify's system for taxes.
If none of the above is relevant to your situation, I encourage you to contact our live support team so that we can investigate this situation in more detail from our end.
To get in touch with our team, you'll need to login to your store via our Help Center here. Once logged in, select a topic that best fits your query or situation. From there, you'll be taken to a page with a list of relevant support articles, and you can scroll to the bottom of that page to select your preferred contact method with our team. Our live support team will be able to assist you further from there.
Kimi | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog