Question: My card bill was due on Monday and I paid on Wednesday night. Can the bank still call it past due and report it to a credit bureau?
Answer: No, if the payment is received within the three-day grace window. In India, card issuers may report a credit card account as past due to credit information companies or levy late-payment charges only when it remains past due for more than three days. The days past due are still counted from the statement due date.

Supporting evidence:
title: rbi.org.in/BS_ViewMasDirections.aspx
quote: Card-issuers shall report a credit card account as 'past due' to credit information companies (CICs) or levy penal charges, viz. late payment charges and other related charges, if any, only when a credit card account remains 'past due' for more than three days The number of 'days past due' and late payment charges shall, however, be computed from the payment due date mentioned in the credit card statement
context: unded interest payment on your outstanding balance" shall be prominently displayed in all the billing statements to caution the cardholders about the pitfalls in paying only the minimum amount due. The MITC shall specifically explain that the 'interest-free credit period' is suspended if any balance of the previous month's bill is outstanding. iv. For this purpose, card-issuers shall work out illustrative examples and include the same in the Welcome Kit sent to the cardholders and also place it on their website. v. v Card-issuers shall report a credit card account as 'past due' to credit information companies (CICs) or levy penal charges, viz. late payment charges and other related charges, if any, only when a credit card account remains 'past due' for more than three days. The number of 'days past due' and late payment charges shall, however, be computed from the payment due date mentioned in the credit card statement, as specified under the regulatory instructions on 'Prudential norms on Income Recognition, Asset Classification and Provisioning pertaining to Advances' amended from time to time. Late payment charges and other related charges shall be levied, only on the outstanding amount after the due date, and not on the total amount due. vi. vi Interest shall be levied only on the outstanding amount, adjusted for payments/refunds/reversed transactions. vii. Changes in charges shall be made only with prospective effect giving prior notice of at least one month.

If a cardholder desires to surrender his/her card on account of any change in charges to his/her disadvantage, he/she shall be permitted to do so without levying any extra charge for such closure, subject to payment of all dues by the cardholder. viii. There shall not be any hidden charges while issuing credit cards free of charge.

7. Billing (a) Card-issuers shall ensure that there is no delay in sending/dispatching/emailing bills/statements and the customer has sufficient number of days (at least one fortnight) for making payment before the interest starts getting charged. In order to obviate frequent complaints of delayed billing, the card-issuer may consider providing bills and statements of accounts through internet/mobile banking with the explicit consent of the cardholder. Card-issuers shall put in place a mechanism to ensure that the cardholder is in receipt of the billing statement. (b) Card-issuers shall ensure that wrong bills are not raised and issued to cardholders. In case, a card