Your Venmo Balance is made up of any payments that you’ve received from friends that you have not transferred to your bank account. You can see how much money is in your balance by going to your profile page, or by tapping the "☰" icon in the upper left hand corner of the app.
When you make a payment, if the amount of the payment is for more than your available balance, it will be funded by your primary funding source.
If you do have enough money in your Venmo balance to cover the payment, it will be pulled from your balance.
Here’s an example:
Let’s say you have $10 in your Venmo balance and want to pay a friend $12. In this case, the entire $12 would be taken from the card or bank account you have set as your primary funding source (Link to Managing Funding sources).
If you wanted to use the $10 in your balance, you can split the payment into two: send $10 from your Venmo balance first, and $2 (which will be taken from your primary funding source).