How do I get the GST number to appear in the header of all the invoices along with other details like the PAN ,company address etc?

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.

Here's how:

1. Go to the Gear icon and select Custom form styles.
2. Click Edit on the invoice template.
3. Select the Content tab.
4. Under the Header section, check the Permanent account number box and enter the details. 
5. Click Done.

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

9326074696