GST return processing: Portal validates and acknowledges returns, confirms ITC after supplier compliance and communicates results. The GST Common Portal validates uploaded returns, issues acknowledgement numbers, and forwards acknowledged returns to Central and State tax authorities. It manages Input Tax Credit matching-confirming ITC to purchasers when supplier returns and tax payment are valid-communicates matching results to taxpayers, auto-populates ITC reversals in the second month after filing, and aggregates cross-credit utilization between IGST and SGST to generate dealer-wise settlement instructions under the IGST model.