Where can I find the TaxJar calculation log file for "Debug Log"?
If the "Debug Log" setting is enabled, log files for checkout calculations can be found inside wp-content/uploads/wc-logs. You'll see a log file prepended with "taxjar".
Additionally, you can review the TaxJar log under WooCommerce > Status on the Logs tab.
To enable logging, go to WooCommerce > TaxJar in your WordPress admin panel. Check "Enable logging" and click the "Save changes" button.