Hello there,
I'm here to share some steps to pay your vendor using donations in the undeposited funds.
When you haven't deposited your donations, the cash will stay in the undeposited funds, and you can pay your vendor using this cash. You'll need to record your cash or your donations first so it will show in the undeposited funds.
Here's how:
- Go to +New and click Bank deposit.

- Select an account, then tick the funds you want to deposit.

- Click the Add fund to this deposit arrow.
- Select a vendor on the Received from column and choose an expense account under the Account column.
- You can also add a Description and Payment Method.
- In the Amount section, enter the amount in negative to minus the amount.
- Check the Amount section in the upper right corner of your screen if the expense subtracts the total amount of your bank deposit.

- Click Save and close.
Moreover, I'm adding this helpful article as your reference in categorizing your transactions in QuickBooks Online: Categorize online bank transactions in QuickBooks Online.
Come back to this post if you have further concerns or follow-up questions about undeposited funds in QuickBooks Online. I'll be here to lend a helping hand. Have a good one!