1. Go to Transactions > Sale > Modify Bill. Press Enter.

2. A Modify window will appear.  Select the options as per the Requirement i.e. bill no, bill date etc.

3. A Sale Book As on window will appear. Press Enter on the selected entry.

4. A Sale Alteration window will appear. Click on Modify to modify the selected bill.

5. A Cursor will wait on the 'Patient F2', keep pressing enter key.

6. Now, In 'Doctor F1', the user will press the 'F1' function key. 

7. A Prescribed by window will appear. Press 'F3' function key on the selected Doctor.

8. A Selected Doctor Detail window will appear.

9. The user can modify details like Code, Address,phone no, etc.

10. Press Ctrl+W to save the details.