Can we add two taxes for a sale item the calculation should be =(1,000 x 2.5%) x 18% then total will be 1,209/50 ?

Hello, @basshashika. Let me help you on adding two sales taxes for a sales item in QuickBooks Online (QBO).
 

To add two sales taxes, you'll need to set up a group sales tax rate. Here's how:

1. Select Taxes from the menu.
2. Go to Sales tax and choose Manage sales tax.
3. Select Add tax. Then, click Add next to Group rate.
4. Enter the Group name.
5. From the first Tax rate drop-down, choose the rates you want to apply. The Applicable on drop-down will be disabled and set to the Net amount by default.
6. From the second Tax rate drop-down, choose the rate you want to apply.
7. From the Applicable on drop-down, choose what the second rate is applicable on: Net amount, Tax amount, or Net + Tax amount.
8. Choose Add.

The group rate will now show on the Group rates tab of the Manage sales tax screen. 

For more information on how QuickBooks calculates sales tax, feel free to read this article: Learn how QuickBooks Online calculates sales tax.

Additionally, QBO has an automated feature for calculating sales taxes incase you'll want to switch from manual to computerized sales tax.

If you have further questions about setting up group sales tax or any other Tax concerns inside QBO, please don't hesitate to include them in the comments below. It's always our pleasure to help. Have a good one.