Hello,
A white page shows up when checkout is selected under Fees in left menu in development version 4.3.1.
The php error log shows a PHP Fatal error -
[18-Aug-2016 00:29:11 Asia/Kolkata] PHP Fatal error: Cannot redeclare getInvoiceRefNumber() (previously declared in C:\xampp\htdocs\openemr\interface\patient_file\pos_checkout.php:80) in C:\xampp\htdocs\openemr\library\billing.inc on line 289
I will fix this along with some other changes. In the meantime try removing the definitions of getInvoiceRefNumber() and updateInvoiceRefNumber() from pos_checkout.php.