What will happen if the details remain mismatched?

As per section 43C (8), the value of a supply relating
to any payment in respect of which any discrepancy is
communicated and which is not rectified by the supplier
in his valid return for the month in which discrepancy is
communicated shall be added to the output liability of
the said supplier, for the calendar month succeeding the
calendar month in which the discrepancy is communicated.
The concerned supplier shall, in whose output tax liability
any amount has been added shall be liable to pay the tax
payable in respect of such supply along with interest, at
the rate specified under sub-section (1) of section 36 on the
amount so added from the date such tax was due till the
date of its payment.