I tried to set up sales tax but i saved without adding the percentage of the tax. Now sales tax is coming out if scope and not letting me change it

You'll have to edit the rate of your added tax to include the percentage through the Tax agencies tab in the Manage sales tax page, sssksharma607.

You're unable to update any QuickBooks Online (QBO) default tax rates. However, if you've set it up manually, follow these steps to edit your sales tax rate:

1. Go to Taxes and select Sales tax.
2. Choose Manage sales tax.
3. In the Tax agencies table, locate the rate you want to change. Then, pick Edit rate under the Make inactive dropdown.
4. In the Edit sales tax rate window, change the rate. You can also change the name if you like.
5. Set the Effective date, if required. This will be the date from which the rate change will take effect.
6. Click Save. 

For more insight about the process above and details on things like what'll happen when you edit the sales tax rate, please see this article: Sales tax rate in QuickBooks Online.

Once all arrangements are in place, you can efficiently manage your sales tax payments within the Tax Centre in QBO.

Please don't hesitate to let us know in the comments if there's anything else you need or concerns about sales taxes in QBO. We're always ready to help you out.