QAB charges in PNB refer to Quarterly Average Balance charges that are levied by the bank if the average balance in a customers account falls below a certain threshold. These charges are applicable every quarter and vary based on the type of account and the minimum balance requirement. The QAB charges are calculated by taking the average balance of the account over a period of three months and comparing it to the minimum balance requirement set by the bank. If the average balance falls below the minimum balance requirement, the customer is charged a penalty fee. The penalty fee varies based on the type of account and the shortfall in the average balance. It is important for customers to maintain the minimum balance requirement to avoid QAB charges and optimize their banking experience.