Yes, you can definitely add more details in your invoice header, s-sayeeharshiny-.
Once you have set up your GST, the GSTIN will directly appear on your invoice template. To set it up, just click the Taxes menu. In addition, you can add your PAN to the template.
For more details in customising your sales forms, you can click here.
Feel free to mention me in your reply if you need more help. Take care!
Pls go to custom forms and styles. You can click on header portion and then tick on all the details you want.
Do let me know if you have query
CA Alok Shah