Self-assessment return payment rules require prior tax, interest, and fee payment with proof before filing and default consequences for shortfall. Self-assessment requires an assessee, before furnishing the return, to pay any tax payable after crediting amounts already paid, tax deducted or collected at source, foreign tax relief, and applicable tax credits, together with interest and fee. The return must be accompanied by proof of such payment, and any shortfall is first adjusted against fee, then interest, and lastly tax. Amounts paid are later deemed to be paid towards regular or other assessment, and non-payment results in default under the Act.