TDS has to be deducted in line with advance tax. There is nothing wrong in deducting the entire tax amount computed in advance. In fact it would be convenient for your client's employer.
Filing of etds return also does not pose any problem at all. For eg: let us say salary for the 1st quarter is 75000/- (April to June) and say tax liability for the entire financial year is Rs. 12500/-. Employer can deduct the tax in any month during the 1st quarter or spreading 12500/- over 3 months of the said quarter.
If the entire tax amount of Rs. 12500/- is deducted in June, then while filing his ETDS return for the 1st quarter he has to prepare the data in following manner:
In deduction sheet of 24q1 (ETDS return) he has to enter Rs. 25000/- in the amount paid column,
Mention Tax deduction date as 30-06-year,
Enter tax paid column with 12500/- ,
total value of concerned challan in challan shet and
link the same to deduction sheet entry mentioned above.
He need not show any deduction details for the said employee in the remaining three quarters (q2 q3 q4).
In q4 returns, only he has to show the details of form 16 in salary sheet provided in q4 returns.
The above procedure is quite acceptable and valid. In fact IT department will be happy if such methodology is adopted. He will get the full credit in his 26AS as single line entry.
It reduces employer's work also.
If employer does not agree for the deduction, alternatively, your client can compute the tax and pay in advance using advance tax challan ITNS-282 to the designated banks quoting his PAN number.
Regards
Ravindra