How do I change "Business Registration Number" with "TIN" on the invoice?

You've come to right place, @schematic-schema.

You can edit your registration number from the company settings. Let me walk you through the steps.

1. Go to Gear, then Account and settings.
2. Click the Pencil icon in the Company name section.
3. Change the registration number. Then, Save.

With these steps, the company information on your invoices will also change. With regard to your tax type, you'll want to enable your GST taxes from the Sales Tax Center. Please refer to this article for more information: How do I set up sales GST/VAT rates and use them on forms? (International QBO).

I've also added our FAQ for GST in QuickBooks Online which I'm sure you'll find helpful. It has answers to common GST questions that'll guide you through the process.

That'll do it. Let me know if there's anything else you need help with. I'll be around to assist you every step of the way. Thanks for joining us today and have a lovely weekend ahead.