What will be the legal position in regard to the reversed input tax credit if the supplier later realises the mistake and feeds the information?

At any stage, but before September of the next
financial year, supplier can upload the invoice and pay
duty and interest on such missing invoices in his GSTR-3 of
the month in which he uploaded the invoice. The recipient
will then automatically get ITC on that invoice. The interest
paid by the recipient at the time of reversal will also be
returned to the recipient through an automated system on
the GSTN.