Transactions can be declined for various reasons. The most common are:
1. The transaction amount exceeds the card balance.
Please ensure that the transaction amount is equal to or less than the available balance.
2. Tip tolerance
At restaurants, hotels, spa salons, and other merchants where it is customary to leave a tip, cards work with a tip tolerance function.
A "tip tolerance" is a security feature that ensures there are sufficient funds on the card for the tip you mark on a receipt, after the server swipes the card. It is usually 20%, by default. The tip tolerance isn't actually charged to your card; rather, the authorization is a kind of “hold” to make sure there are enough funds to cover the tip, if you choose to leave one.
Please note that while you will not be charged this amount nor will you lose any money, in these cases you will only be able to use 80% of the available card amount. The remaining 20% can be used later; it will be returned to your card within 7 business days.