The main change is the obligation to make a correction of the tax deductible costs (transfer into non deductible costs) in case of lack of payment of the invoice or other document within 30 days from the date of expiry of the due date agreed by the parties. If the due date is longer than 60 days - in case of lack of payment of it within 90 days these costs must be transferred into non deductible costs. These amendments do not concern the tax payer who classified costs connected with not paid invoice as non deductible costs at the beginning.

Should the amount of the invoice or other document be classified to deductible cost before 1 January 2013, the new regulations will not apply to it, even if the payment is due in 2013.