What is the time limit for issue of debit/credit note(s) for revision of prices?

The taxable person may issue the debit/credit note(s)
or a supplementary invoice within 30 days of the price
revision.
In case where the price is revised downwards the taxable
person shall be allowed to reduce his tax liability only if the
recipient of the invoice or credit note has reduced his ITC
corresponding to such reduction of tax liability – section
153.