dev/core#1972 Fix tax_amount calclation on renewal form

[eileenmcnaughton]

Overview

Fixes a regression whereby the tax_amount was incorrectly calculated on the membership renewal form

Before

Tax (for a 10% rate) was calculated as

tax = totalAmount * .10

After

tax = totalAmount - (totalAmount / 1.1)

Technical Details

If the PR involves technical details/changes/considerations which would not be manifest to a casual developer skimming the above sections, please describe the details here.

Comments

@KarinG has detailed this well in https://lab.civicrm.org/dev/core/-/issues/1972

We should backport this once merged

[civibot]

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[KarinG]

Documenting that I've tested this extensively - have had this in our repo for >48h - it fixes renewal with Tax issues:

[karin@ectemnia BAO]$ git diff Order.php.DIST Order.php
diff --git a/CRM/Financial/BAO/Order.php b/CRM/Financial/BAO/Order.php
index cb43851..1faea92 100644
--- a/CRM/Financial/BAO/Order.php
+++ b/CRM/Financial/BAO/Order.php
@@ -248,7 +248,7 @@ class CRM_Financial_BAO_Order {
       if ($this->getOverrideTotalAmount() !== FALSE) {
         if ($taxRate) {
           // Total is tax inclusive.
-          $lineItem['tax_amount'] = ($taxRate / 100) * $this->getOverrideTotalAmount();
+          $lineItem['tax_amount'] = ($taxRate / 100) * $this->getOverrideTotalAmount() / (1 + ($taxRate / 100));
           $lineItem['line_total'] = $lineItem['unit_price'] = $this->getOverrideTotalAmount() - $lineItem['tax_amount'];
         }