Refund entitlement under section 237 requires an assessment before claim and is subject to assessment time limits. Refund entitlement under section 237 requires a filed return of total income and an assessment or order of assessment by the ITO; only after the ITO computes total income and determines tax properly chargeable can an excess payment be refunded, and refund claims are subject to the same statutory time limits for making assessments, including a one-year extension where the return is filed on the last permissible date.