QuickBooks 6123 is a common error that occurs within the Desktop edition of the software. It could prevent you from opening your company files due to various reasons. To start resolving it, you should try to close all QuickBooks related background processes, and then restart the application. In case this doesn’t work, you can also try to use the QuickBooks File Doctor Tool. If you think you require the help of an IT professional, you are welcome to contact the QuickBooks Error Xpert at our QuickBooks error support number 1-888-986-7735 or visit our website.