Additional income tax on updated returns required at filing alongside tax and interest obligations. Section 140B requires payment of tax, interest, fees and an additional income tax at the time an updated return under proposed section 139(8A) is furnished. Where no earlier return exists, tax is computed after accounting for advance tax, TDS/TCS, section 89 reliefs, specified foreign tax reliefs and certain tax credits, and interest under section 234A is computed on tax declared in the updated return. Where an earlier return exists, tax and interest are computed after accounting for credits and omissions in the earlier return and reduced by interest already paid; payment proof must accompany the updated return.