It could be taxing times for tax officials as well as those they turn their glare on. They have been told by the chief of the Central Board of Direct Taxes (CBDT), the apex body, to target and impose tax on Rs 3 lakh crore deposits which is estimated to be the quantum of unexplained cash parked with banks after demonetisation was announced.

CBDT chairman Sushil Chandra conveyed the message in a recent video conference to senior officials of I-T department, according to two persons who attended the meeting.

Identifying a sizeable slice of deposits as unaccounted cash will not only shore up overall direct tax collection in a slowing economy, but also give the government a chance to showcase the success of demonetisation, which has been blamed by the Opposition for the dip in growth.

Tax authorities technically have the power to come down heavily on those who are unable to explain their cash deposit by slapping 60 per cent tax and penalty. But such a process, entailing a case-by-case scrutiny, could be tedious and time consuming.

"It's unclear how the Rs 3 lakh crore number has been arrived at... even if it is a fairly accurate estimate, which it probably is, the department will take about two years before it begins to verify the explanations (that depositors offer). In next few months, the assessments pertaining to notices which were sent in September 2015 (for the financial year 2014-15) will have to be dealt with as these will get time-barred in December 2017," said a person familiar with the matter.

"Next, the assessments related to notices for financial year 2015-16 which will get time-barred in December 2018 will be taken up... only after these are done, the department will be in a position to pursue cases for 2016-17 when the demonetised cash was deposited. Otherwise, where's the manpower?" the person said.

Under the circumstances, unless the tax office is able to assign and dedicate officers to quicken the procedure for taxing these dubious deposits, it would not result in a higher collection this year.

With 99 per cent of the Rs 15 lakh crore worth de-legalised currency notes finding their way back to RBI, it was widely perceived that a large number of cash hoarders have used banks to launder their black money in November and December 2016.

"The chairman, CBDT," said the Board spokesperson, "has directed the officers to work for achievement of Budget Estimates for 2017-18 which requires a growth of 15.3 per cent ." Asked whether the tax collection targets appear unrealistic with the economy growing at a nominal rate of less than 9 per cent , the CBDT official said, "The targets have been fixed considering the overall growth of the economy, effect of demonetisation and arrear demands of the department."

A higher personal income tax collection could to an extent cushion a slower growth in corporate tax if the slowdown in the economy continues.

"Corporates will have a clearer picture about earnings in the third and fourth quarter. At that point, tax numbers may go up or down depending on sales and performance. So, if GDP growth stays sluggish, a higher tax from corporates cannot be expected," said a tax officer. On the estimate of Rs 3 lakh crore, there was no comment from the CBDT official till the time of going to press.

Three senior tax practitioners ET spoke to alleged that since August, the department is holding back tax refund in order to meet the stiff collection target, but this was denied by the CBDT spokesperson.