What is the procedure adopted for making the assessment under section 143(1)?
Assessment under section​ 143(1) is like preliminary checking of the return of income. At this stage, the total income or loss is computed after making the preliminary adjustments (as discussed i​n previous FAQ). The other procedures in this regard are as follows:

After making the adjustments (if any) as discussed in previous FAQ, the tax, interest, and fee if any, shall be computed on the basis of the adjusted income.
Any sum payable by the taxpayer or refund due to the taxpayer shall be intimated to him.
An intimation shall be prepared or generated and sent to the taxpayer specifying the sum determined to be payable by, or the amount of refund due to him.
An intimation shall also be sent to the taxpayer, in a case, where the loss declared in the return of income by the taxpayer is adjusted but no tax or interest is payable by, or no refund is due to him.
No intimation will be sent to the taxpayer in a case where no sum is payable or refundable or no adjustment is made to the returned income. In such a case, the acknowledgement of the return of income shall be deemed to be the intimation.
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*As per section 234F, a fee shall be levied where the return of income is not filed within the due dates prescribed under section 139(1). Fee for default in furnishing return of income shall be Rs. 5,000 if return has been furnished after the due date prescribed under section 139(1). However, it shall be Rs. 1,000 if the total income of an assessee does not exceed Rs. 5 lakh.