In case of dissolution, bankruptcy, cancellation and other termination of production and operation in the middle of the year, taxpayers should declare to the competent tax authorities before liquidation, and make final settlement and payment within 60 days from the date of actual termination of operation, so as to settle the payable and refundable enterprise income tax; Taxpayers who terminate their tax obligations according to law under other circumstances shall, within 60 days from the date of stopping production and operation, handle the final settlement of enterprise income tax for the current period with the competent tax authorities.

So it is usually before May 3 1 every year.