how can I connect withholding tax on purchases?

We'll have to turn on the VAT function so we can start collecting taxes on sales and purchases, hicham. Also, I'll guide you on how to set up the VAT rates specific for purchases.

We can easily follow the Step 2: Tell QuickBooks where you collect VAT section of this article to activate the feature: Set up and use VAT in QuickBooks Online.
 

With that, here's how to set up a tax rate specific for purchases:

1. In the VAT page, click the Add tax button.
2. Select Tax rate and enter the Tax name.
3. Fill in the Description if necessary.
4. Mark the Purchases tick box and set the Purchase rate.
5. Enter the Account and set the Show tax amount on return line.
6. Click Save.

When we create Expenses, Bills, or Cheques, we will now have the option to collect withholding VAT.

From there, we'll know how much VAT we owe and file the VAT returns.

Let us know if you have additional queries on how to handle your taxes in QuickBooks Online.