Challan Details are mandatory in case of Payment/ Deduction where TDS is deducted from the payment. It is important to add challan details to payments while filing e-TDS return so that correct tax credit reflects to correct payee/ deductee. However, no need to add challan details to payments where no TDS is deducted.    

In case of mismatch in challan and Payment details, Payer/ Deductor can modify details by filing an online correction through TRACES.   

Read More: How to modify deductee details in filed e-TDS Return?