Accounting and returns under gst regime

Hello,

Recently the goods worth of Rs.4 Lakhs(for which amount sale bill was also issued) of my client seized by GST department and they had done the valuation to Rs.836000 and my client had paid IGST and Penalty for the same considering 836000 as taxable value.

Now the portal is showing IGST balance in cash ledger.

My question is how to deal with this case in accounting as well as GSTR-3B. Whether full credit is allowable or not?

As party will pay Rs.4 Lakh only for which bill was issued however vaulation and tax is paid on 836000.

Also consider the income tax aspects please!

Thanks in advance