B2C SALE NOT SHOW IN GST

sir

my client send me his sales bills monthly which I show in GST and it's match between 3B and GSTR1 but this time he ask me to file his ITR also so when u check his bank statement there is much more amount receive in bank than he show in bills when I ask him he said that this b2c transaction which amount received through scanning QR code now what I do

Can I show this b2c sale in July return and pay tax and interest in it and how I show that this is not this year sale but last year sale which I showing now

please help and suggest