When you buy an item at a store with a bank transfer or credit card, you are promising that the money is available in your account. The store doesn't receive the money for up to 3 banking days later.
Sending a bank transfer deposit to TransWorld Courier Ltd works exactly the same way. To ensure payment, TransWorld Courier Ltd waits until the money is deposited into our trust account, which is then considered "good funds." This takes longer, but gives Buyers and Sellers an extra level of security.