We need to integrate QB to income tax system (uganda) for issue sales invoices. Can we do this without third party application?

Yes, you can definitely integrate Uganda's income tax system with QuickBooks, @userthilinab214.

You can set it up by going to the VAT menu on your QuickBooks Online company. I can provide you with the steps:

1. From the left pane, open the VAT menu.
2. Click on Set up VAT, then select Next.
3. Choose a Start of tax period from the drop-down.
4. Choose a Filing frequency.
5. Select a Reporting method by clicking the radio button.
6. Enter the VAT number.
7. Once done, click on Next then Ok.

That should be all in setting up your income tax. Once ready, feel free to review this guide on how you can handle invoices in QBO: Create and send an invoice in QuickBooks Online.

You already know where to find me. Just comment below if you need extra help with handling taxes or invoices. I'll be around to back you up anytime. Have a good one and stay safe!