I need to add the company stamp and the signature for the invoice. please guide

It's nice to see you here in the Community, geethika-p-meral.

Adding the company stamp and signature on an invoice is currently unavailable. 

You can use the Attachments box to include an image of your signature or to add a company stamp. I'll show you to accomplish it:

1. Go to the + New icon, then select Invoice.
2. Fill in the necessary required fields. 
3. Then add the signature or image under the Attachments section.
   

Another option is to look for a third-party application that lets you do the tasks. You can find one from the Apps menu within your account that suits your business needs.

If you need help personalising your sales forms and adding specific info, check out these links for reference:

• Customise invoices, estimates, and sales receipts in QBO
• Capture signatures using the QBO app

Keep me posted if you have other concerns. I've got your back.