When you use your debit card to make a purchase, the merchant’s payment system will perform what is called an authorization. This is where your transaction gets an approval and reserves funds from your account to pay the merchant. Certain point of sale systems may request authorization for more than the final transaction amount to account for things such as taxes, gratuity, or if you swipe your card before you use the service, like at the gas pump.
You may be able to avoid some of these scenarios by seeing if the merchant has the option for you to pay the full amount using your PIN to complete the transaction. Not all merchants will offer this option so you may have to accept the authorization or consider using a different payment method.
Once the transaction posts to your account and is no longer pending it will reflect the final purchase amount. In some cases the authorized amount may be less than the final purchase amount so you should make sure you have enough funds in your account to cover the final transaction amount.
Pending transactions can post to your account as early as the following business day but can take longer depending on the merchant’s payment processing systems. The normal time for a pending transaction to post is 3 business days.