If you've reported less outward supply in your GSTR-1 and GSTR-3B for the 2017-18 financial year and haven't made provisions in subsequent years, you can correct this in your pending GSTR-9 annual return. You'll need to add the missing outward supply amount and pay the differential tax along with applicable interest using Form DRC-03.
I have shown less amount of outward supply in gstr 3b & 1 returns of financial year 2017-18. And we had not made any provision/payment of the same in a subsequent years. Our GSTR9 return is still pending to complete.
Can we add remaining part of outward supply in GSTR9 and pay tax on increased amount of supply ?