Dear Mr. Ashok,
As per my view
Section 43B starts with the words "Notwithstanding anything contained in any other provision of this Act, a deduction otherwise allowable under this Act in respect of - any sum payable by the assessee by way of tax, duty, cess or fee, by whatever name called, under any law for the time being in force......." , Before discussing the allowance or disallowance of Service Tax due to non-payment, it is important to know the method of accounting followed by subject entity. If the method of accounting followed by the entity is mercantile system then in any case service tax will no be routed through Profit and Loss account and the subject entity would not have claimed it as deduction in computation of Income. In mercantile accounting system Service Tax payable account and Service Tax Receivable/CENVAT account are reflected in balance sheet only.
Applying Section 43B with non-payment of service tax in case of mercantile accounting system. Section 43B specify "a deduction otherwise allowable under this Act". In mercantile accounting system service tax is not routed through P & L and therefore non payment of service tax will not be added to your computation of income in the assessment.
If the method of accounting is different and earlier the deduction has been claimed then Section 43B will be attracted.
For details refer: -
Delhi High Court
Cit vs Noble And Hewitt (I) (P) Ltd.
[2008] 305 ITR 324 (Delhi)