1. Go to Settings-->Settings-->Process Configuration option
2. A process configuration screen will appear in which process name & process type drop downs are there
3. Select Invoice in the process name drop down and CompanyAsLetterhead in the process type drop down
4. Save the details
5. Go to Accounts-->Accounts--Invoice Details
6. Search for the invoice to be printed
7. Click on Print button
8. A pop-up opens "Do you want to print on preprinted Stationery" with Yes or No buttons
9. Click on No button
10. An invoice will print with proper letter head in the header