Assessment under section 143(1) sets preliminary return adjustments and issues intimation of tax or refund liability. Assessment under section 143(1) is a preliminary scrutiny where adjusted total income is computed, tax, interest and applicable fees are calculated on that adjusted income, and an intimation is sent specifying tax payable or refund due. If a declared loss is adjusted, an intimation is issued even when no tax or refund follows. Where no adjustment occurs and no sum is payable or refundable, the return acknowledgement is deemed to be the intimation. A late filing fee is imposed for delayed returns, with a lower fee applied where income is at or below a specified lower threshold.