I’ve added new custom field as serial no. but its showing in bottom of the page how can I change the position to below item description?
You can’t create custom field as a column for line items.
What are you selling? Are you using inventory module?
yes i am selling computer items so i need to add serial numbers on invoice report …
I dont think that is possible, custom feilds showing on the final report is one of the features i am dying to see. For instance I send Bills to Donors on behalf of a friend using manager, I need to let the invoice show ‘Service Order Number’, a custom feild we created but it never shows on the invoice itself 
If you are selling inventory items, then set them up under Inventory items. Selling them will show SKU on line item. For non-inventory items, you can use Sales Invoice Items under Settings tab.
No need for custom fields.