GST NUMBER DOESNT SHOW ON INVOICE

Welcome to the Community, @manish-mittal-pa. I'll be glad to help you with your GST number to show up on the invoice.

1. Go to the Gear icon.
2. Select the Custom Form Styles tab.
3. Click Edit and choose the Content page.
4. From the right section, click the pencil icon to open the custom form.
5. Tick the Customer GSTIN checkbox.
   
   

Please refer to this article for more details: Customise invoice for GST.

Additionally, please check out this article for the complete process to set up your GST in QuickBooks Online: Setting up QuickBooks for GST.

I'll be around if you need more help or if you have clarification with showing up your GST on the invoice. Have a great day ahead!