A deductor would face the following consequences if he fails to deduct TDS or after deducting the same fails to deposit it to the credit of Central Governments account:-
a) Disallowance of expenditure
As per section 40(a)(i) of the Income-tax Act, any sum (other than salary) payable outside India or to a non-resident, which is chargeable to tax in India in the hands of the recipient, shall not be allowed to be deducted if it is paid without deduction of tax at source or if tax is deducted but is not deposited with the Central Government till the due date of eTDS filing.
However, if tax is deducted or deposited in subsequent year, as the case may be, the expenditure shall be allowed as deduction in that year.
Similarly, as per section 40(a)(ia), any sum payable to a resident, which is subject to deduction of tax at source, would attract 30% disallowance if it is paid without deduction of tax at source or if tax is deducted but is not deposited with the Central Government till the due date of filing of return.
However, where in respect of any such sum, tax is deducted or deposited in subsequent year, as the case may be, the expenditure so disallowed shall be allowed as deduction in that year.
b) Levy of interest
As per section 201 of the Income-tax Act, if a deductor fails to deduct tax at source or after the deducting the same fails to deposit it to the Governments account then he shall be deemed to be an assessee-in-default and liable to pay simple interest as follows:-
(i) at one per cent for every month or part of a month on the amount of such tax from the date on which such tax was deductible to the date on which such tax is deducted; and
(ii) at one and one-half per cent for every month or part of a month on the amount of such tax from the date on which such tax was deducted to the date on which such tax is actually paid.
c) Levy of Penalty
Penalty of an amount equal to tax not deducted or paid could be imposed under section 271C.
Source: Income Tax