An important character of SAP Business One is that you cannot change or cancel any document of journal entry once you added them. The only way is to create another document and hedge the accounting. The best way to aviod this problem in SAP Business One is to use Journal Entry Preview, which allow you to preview the journal entry and change the document if required.
Use Preview before you adding document
Click the Journal Entry Preview icon in the toolbar.
The Journal Entry Preview shown up looks just like usual Journal Entry, but here you can preview the and adjust the document if needed.
For version SAP Business One 9.1, version for SAP HANA PL06 and SAP Business One 9.1 PL06, Journal Entry Preview can also display a separate line for each documents row.
Just choose: Administration > System Initialization > Document Settings, and click the box, “Disable Journal Entry Lines Grouping in Posting Preview”.