Case study regarding less output liability paid

Komal Kumari (38 Points)

19 August 2021  
a supplier raised invoice to his customer with Rs. 50000 in F.y 18-19 but uploaded in his GSTR-1 only 45000. his customer taken input with whole amount like that 50000 in f.y 18-19. what can I do?? how to resolve this problem in f.y 21-22.