How to customise the purchase bill format. I want to add a discount column and TCS tax in India

Welcome to the Community, agrawaldevansh4-.

In QuickBooks Online, customizing purchase bills is unavailable. You can only customize invoices, estimates, and sales receipts. 

However, I've got some steps you may consider doing. You'll want to create an Income account as "Discount Received" under the income category in the Chart of accounts. 

1. Go to Settings and select Chart of Accounts.
2. Click New.
3. In the Account Type ▼ dropdown, choose an account type.
4. In the Detail Type ▼ dropdown, select the detail type that best fits the transactions you want to track.
5. Click Save and close.

When you create a purchase bill, select the Discount Received account from the Category details, and ensure to enter the discount amount as a negative amount. 

That should do it! Fill me in if there's anything you want to ask. I'll be glad to assist you more.