For an offence, usually what is important is that there must be mens rea or a guilty mind. This means that there should be some type of mala fide intention of doing something wrong to someone. If you are doing some act without any wrong intention or without the intention of causing a wrongful gain to yourself or a wrongful loss to someone else, it may not be an offence. This is the general rule in criminal law.
In the situation cited by you, when someone is himself permitting the use of his credit card or debit card and authorizing it for withdrawing money from ATM or for buying something online, it may not be an offence, since it is with permission of the card holder from whose account the money would be debited or who would have to pay the charges. In fact, it is a common practice and a large number of people give their debit card or credit card to their family members (or sometimes, to friends) for withdrawing money from ATM etc. It is not an offence when it is done specifically with the permission or authority of the card holder. It is an offence only when you steal someone’s debit / credit card, or use it, without his permission in order to commit a fraud or some other offence.
At the same time, such use of the debit card or credit may be a violation of the terms and conditions of the bank which has issued the card. Usually, these terms may restrict the usage of card by other people. The bank may not take any legal action against you, but there may perhaps be a penalty or the bank may perhaps cancel the card (of course, one has to check what exactly are the bank’s terms and rules in this regard). However, this is also unheard of. Banks may unofficially be happy if the card is used more because they may be earning commission on card usage, so even it is a violation of their terms, the banks may not generally complain, if the card is being used with your permission and you are not objecting to it.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.