When you look at your sold items, it will tell you if the item is paid for or not. If is says Paid, then it should be safe to ship the item. If it says the sale is Unpaid, wait until the payment clears. PayPal will say Pending and gives you a date that the payment should clear. Make sure that you notify the customer that you will ship the item once the payment has cleared, and keep checking PayPal to see if it is still pending. The date they give you is usually accurate, but always check to make sure before shipping.