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Create a custom tax rule to override AvaTax calculations

This article applies to:AvaTax

Create a custom tax rule to override the way AvaTax calculates tax on your transactions.

A warning icon


  • AvaTax doesn't keep custom tax rules up to date. You need to keep them up to date on your own.
  • Custom tax rules are not applicable to transactions in volunteer Streamlined Sales Tax (SST) states.


Before you begin

If the rule you want to create applies to a custom tax code, you must create the custom tax code first.


  1. In AvaTax, go to Settings > All AvaTax Settings.
  2. Next to Custom Rules, select Manage.
  3. Select Tax Rules and then select Add a Tax Rule.
  4. Enter the rule information on the New Custom Rule page.
    • Enter a descriptive name that makes the rule easy to find.
    • Select an effective date when the rule should start applying to your transactions. Select an expiration date if this rule should only be used for a certain period of time.
    • Select the custom rule you want to apply.
      • Taxability Rule: Changes whether an item is or is not taxed within a specific jurisdiction.
      • Exempt Entity Rule: Changes whether or not a customer is exempt from tax.
      • Rate Override: Changes the rate at which an item is taxed.
      • Base Override: Changes the amount of an item's price that is considered taxable. 
  5. Enter the taxability details under Applicability. Enter the information AvaTax should use when applying your tax rule, including which tax code the rule applies to.

    Custom tax rules can only be applied to one location at a time. Create a rule for each location where you want to apply the rule.

  6. Select the tax treatment details and options AvaTax should use when applying your tax rule. These options vary depending on the type of rule you choose.
    • Taxability Rule
      1. Select whether this rule makes an item taxable or non-taxable.
      2. Select the jurisdiction this rule applies to.
      3. Select whether the tax rate should be based on the ship-from address (origin), ship-to address (destination), or if AvaTax should decide (use system sourcing).
    • Exempt Entity Rule
      1. Select whether this rule makes the customer taxable or exempt.
      2. Select the jurisdiction this rule applies to.
    • Rate Override
      1. Enter the rate you want to use.
      2. Select whether the rule includes special handling and enter either a cap or threshold value if your selection requires it.
      3. Select the jurisdiction this rule applies to.
      4. Some countries have alternate VAT rates for different products, services, or types of business. If this rule is overriding a specific VAT rate instead of standard sales or sellers use tax, choose the rate from the Rate Type dropdown.
    • Base Override
      1. Enter the percentage of the item's price that you want to be taxable.
      2. Select the jurisdiction this rule applies to.
  7. Select Save Tax Rule.

Your new custom tax rule applies to your transactions going forward. You can apply your rule to past transactions by saving sale data again or recalculating the tax.

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