<h1>GSTR-3B input tax credit and RCM claims to face portal blocks if ledger mismatches cause negative balances</h1> GSTN will shortly enforce portal validations to prevent negative balances and excess input tax credit (ITC) availment against the Electronic Credit Reversal and Re-claimed Statement and the RCM Liability/ITC Statement while filing Form GSTR-3B. Reclaimed ITC in Table 4(D)(1) must not exceed the sum of the Reclaim Ledger closing balance and current-period ITC reversed in Table 4(B)(2); otherwise, GSTR-3B filing will be blocked. RCM ITC in Tables 4(A)(2) and 4(A)(3) must not exceed the sum of current-period RCM liability paid in Table 3.1(d) and the RCM Ledger closing balance; otherwise, filing will be blocked. Where either ledger shows a negative closing balance, filing will be disallowed until the excess is reversed (with any shortfall added as liability) or equivalent RCM liability is paid or ITC claim is reduced.