In PayPal Shipping Center, refunds for voided labels and USPS adjustments for overcharged labels are stored in your account as available Account Credits.
Account Credits are automatically used first to fund your label purchases. Learn how to add or change your payment method to fund your labels.
If an Account Credit does not cover the full cost of a label, the difference will be deducted from your PayPal account.
On the Buy a Label screen, you will see your total Account Credits amount. The total amount owed for the label will be in the green Purchase Label button.

To view your available Account Credits: