GSTR-3B is a monthly self-declaration return that every registered GST taxpayer must file. It summarizes the total outward supplies, input tax credit (ITC) claimed, and tax liability for the period. Unlike GSTR-1, it does not require invoice-level details but provides a consolidated summary. The return must be filed even if there are no transactions in a given period. Non-filing of GSTR-3B leads to penalties and interest on the unpaid tax amount. The due date for GSTR-3B filing is the 20th of the following month for taxpayers with turnover above ₹5 crore. Small taxpayers under the Quarterly Return Monthly Payment (QRMP) scheme can file GSTR-3B quarterly. However, QRMP taxpayers must pay taxes every month using a challan. Input tax credit (ITC) claims in GSTR-3B must match the auto-generated GSTR-2B statement. Taxpayers must ensure that ITC is only claimed for eligible purchases as per GST rules. Any excess ITC claimed must be reversed in the subsequent returns. Late filing of GSTR-3B attracts a late fee of ₹50 per day for normal returns and ₹20 per day for nil returns. Interest at 18% per annum is charged on delayed tax payments. GSTR-3B must be filed before the due date to avoid disruptions in GST compliance. The GST portal does not allow filing of GSTR-1 if GSTR-3B for the previous period is pending. Tax payments can be made through electronic cash ledger or electronic credit ledger. The return includes details of taxable sales, exempt supplies, and non-GST outward supplies. Taxpayers must report details of reverse charge mechanism (RCM) liability in GSTR-3B. Any excess tax paid can be adjusted in future returns or claimed as a refund. GSTR-3B helps in tax reconciliation and prevents mismatches in ITC claims. Errors in GSTR-3B can be rectified in subsequent months but cannot be revised directly. The return acts as a bridge between input tax credit and tax liability. GST authorities use GSTR-3B data to detect mismatches with GSTR-1 and GSTR-2B. E-commerce operators must report their tax liability separately in GSTR-3B. The return also captures details of TDS and TCS under GST for applicable taxpayers. Large businesses automate GSTR-3B filing using ERP software integrated with GSTN. GST refunds for exports and inverted duty structure cases depend on GSTR-3B data. Taxpayers can track their past GSTR-3B filings and payment status on the GST portal. Filing accurate GSTR-3B ensures smooth compliance and reduces chances of scrutiny.