Return filing deadline under section 139 clarifies eligibility for section 11 exemption for registered trusts when timely filed. The insertion of clause (ba) in sub section (1) of section 12A requires that a person in receipt of income chargeable to tax must furnish the return of income within the time allowed under section 139 for a trust registered under section 12AA to avail exemption under section 11; returns required by sub section (4A) must therefore be filed within the time allowed under section 139 and assessments denying exemption solely for belated filing should be rectified.