For Cougar Mountain Software Support's Professional Version (V2012, V2011, V2010, V2009, V12-V6)
Answer: This is caused by a corrupted register code.
Create a new register code: 1. Open the Point of Sale module. 2. Select options. 3. Click on codes. 4. Select register codes. 5. Create a new register code and save.
It may be necessary to clear the sales from the old register and enter the sales into the new register to be able to post.