Fix - Non-taxable product no longer zeroes shared standard tax rate (WOOTAX-240)

In a cart mixing a taxable product and a non-taxable one (Tax Status =
"None", Tax Class = "Standard"), taxes stopped calculating for the whole
cart. get_itemized_tax_rates() writes one WooCommerce tax rate row per
TaxJar breakdown line item, keyed by the product's Tax Class. The
non-taxable product is sent to TaxJar as exempt (code 99999) so its
breakdown line comes back at 0%, but its Tax Class is still Standard — so
create_or_update_tax_rate() overwrote the shared Standard rate row (already
populated by the taxable product) with 0%, zeroing tax for every standard
item. The zeroed row persisted in wp_woocommerce_tax_rates, which is why
adding another taxable product did not restore it.

Skip rate-row writes for line items whose product has Tax Status "None".
WooCommerce already applies no tax to such products, and this leaves the
shared class rate intact for genuinely taxable items. Zero-rate *class*
products are unaffected (they own a separate rate row).

Note: the tax status check in get_line_items() is not the cause — a
tax_status "none" product is already correctly sent as code 99999. The
defect was downstream, in how the itemized rate rows are written.

Adds a regression test driving get_itemized_tax_rates() with a mixed
taxable/exempt breakdown; it fails on trunk (exempt line writes/zeroes the
shared row) and passes with this fix.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: bartech

changelog.txt

@@ -4,6 +4,7 @@
 * Fix   - TaxJar tax lines wiped when REST API order update includes address change.
 * Fix   - Prevent fatal error on sites running WooCommerce versions without StoreApi support.
 * Fix   - Prevent unbounded growth of WooCommerce tax rate rows when checkout city contains a semicolon.
+* Fix   - Calculate tax correctly for carts mixing taxable and non-taxable products, so a non-taxable product no longer resets the standard tax rate to zero.
 
 = 3.6.7 - 2026-07-06 =
 * Fix   - Prevent fatal error on Atomic sites caused by incorrect path resolution when loading the API client class.

classes/class-wc-connect-taxjar-integration.php

@@ -1735,6 +1735,17 @@ private function get_itemized_tax_rates( $taxes, $taxjar_taxes, $options ): arra
 					$tax_class = $this->backend_tax_classes[ $product_id ];
 				}
 
+				// A product with Tax Status = "None" is exempt from tax but can still
+				// carry the standard Tax Class. TaxJar returns a 0% breakdown line for
+				// it, and because tax rate rows are keyed by tax class, writing that 0%
+				// overwrites the shared class rate used by genuinely taxable products in
+				// the same class — zeroing tax for the whole cart. Skip rate-row writes
+				// for non-taxable products; WooCommerce already applies no tax to them.
+				// See WOOTAX-240.
+				if ( $product && 'none' === $product->get_tax_status() ) {
+					continue;
+				}
+
 				$_tax_rates = (array) $line_item;
 				$priority   = 1;
 				foreach ( $_tax_rates as $tax_rate_name => $tax_rate ) {

readme.txt

@@ -74,6 +74,7 @@ This plugin relies on the following external services:
 * Fix   - TaxJar tax lines wiped when REST API order update includes address change.
 * Fix   - Prevent fatal error on sites running WooCommerce versions without StoreApi support.
 * Fix   - Prevent unbounded growth of WooCommerce tax rate rows when checkout city contains a semicolon.
+* Fix   - Calculate tax correctly for carts mixing taxable and non-taxable products, so a non-taxable product no longer resets the standard tax rate to zero.
 
 = 3.6.7 - 2026-07-06 =
 * Fix   - Prevent fatal error on Atomic sites caused by incorrect path resolution when loading the API client class.

tests/php/test-class-wc-connect-taxjar-integration.php

@@ -1865,4 +1865,88 @@ public function test_create_or_update_tax_rate_does_not_duplicate_rows_for_semic
 			$this->assertStringNotContainsString( ';', $city, 'Tax rate city stored with a semicolon — `_update_tax_rate_cities()` will split it and break find_rates() on subsequent lookups.' );
 		}
 	}
+
+	/**
+	 * A non-taxable product (Tax Status = "None") that shares the standard Tax
+	 * Class with a taxable product must not zero out the shared Standard rate row.
+	 *
+	 * TaxJar returns a 0% breakdown line for the exempt product (sent as code
+	 * 99999). Because rate rows are keyed by tax class — and Tax Status "None"
+	 * does not change the Tax Class — that 0% would overwrite the same Standard
+	 * row the taxable product just populated, zeroing tax for the whole cart.
+	 * Regression for WOOTAX-240.
+	 */
+	public function test_get_itemized_tax_rates_non_taxable_line_does_not_zero_standard_rate() {
+		$taxable_product = WC_Helper_Product::create_simple_product();
+		$taxable_product->set_tax_status( 'taxable' );
+		$taxable_product->set_tax_class( '' );
+		$taxable_product->save();
+
+		$exempt_product = WC_Helper_Product::create_simple_product();
+		$exempt_product->set_tax_status( 'none' );
+		$exempt_product->set_tax_class( '' );
+		$exempt_product->save();
+
+		$taxable_id  = $taxable_product->get_id();
+		$exempt_id   = $exempt_product->get_id();
+		$taxable_key = $taxable_id . '-taxable_item';
+		$exempt_key  = $exempt_id . '-exempt_item';
+
+		// Taxable line is listed first, so without the fix the exempt line would
+		// overwrite the shared Standard rate row to 0% afterwards.
+		$taxjar_taxes = (object) array(
+			'freight_taxable' => 0,
+			'has_nexus'       => 1,
+			'rate'            => 0.0725,
+			'jurisdictions'   => (object) array(
+				'county' => '',
+				'city'   => '',
+			),
+			'breakdown'       => (object) array(
+				'line_items' => array(
+					(object) array(
+						'id'                => $taxable_key,
+						'combined_tax_rate' => 0.0725,
+						'state_tax_rate'    => 0.0725,
+					),
+					(object) array(
+						'id'                => $exempt_key,
+						'combined_tax_rate' => 0.0,
+						'state_tax_rate'    => 0.0,
+					),
+				),
+			),
+		);
+
+		$options = array(
+			'to_country' => 'US',
+			'to_state'   => 'CA',
+			'to_zip'     => '90210',
+			'to_city'    => 'Beverly Hills',
+		);
+
+		$result = $this->invoke_protected_method(
+			'get_itemized_tax_rates',
+			array(
+				array(
+					'rate_ids'   => array(),
+					'line_items' => array(),
+				),
+				$taxjar_taxes,
+				$options,
+			)
+		);
+
+		// The exempt line must not create or update any tax rate row.
+		$this->assertArrayNotHasKey( $exempt_key, $result['rate_ids'], 'Non-taxable line item should not write a tax rate row.' );
+
+		// The taxable line's Standard rate row must remain at 7.25%, not clobbered to 0.
+		$this->assertArrayHasKey( $taxable_key, $result['rate_ids'] );
+		$taxable_rate_id = $result['rate_ids'][ $taxable_key ][0];
+		$rate_data       = WC_Tax::_get_tax_rate( $taxable_rate_id );
+		$this->assertSame( 7.25, (float) $rate_data['tax_rate'], 'Standard rate row was zeroed by the non-taxable line item (WOOTAX-240).' );
+
+		WC_Helper_Product::delete_product( $taxable_id );
+		WC_Helper_Product::delete_product( $exempt_id );
+	}
 }