If you live in Quebec, or in Canada for that matter, you might be using Canpar to ship your products. They have built a plugin for the eCommerce solution, WooCommerce. However, I was having a problem with the shipping plugin calculating taxes properly for the shipping charges as you can see here:
The solution I found was to open canpar-rc.php and on line 495 add [$index] to line 495:
‘taxes’ => $taxes[$index],
That appears to have fixed the problem. Happy coding!