Section 40(a)(ia) of the Income Tax Act

Interest paid on borrowed funds cannot be disallowed merely because the assessee made interest-free advances, provided those advances were made for business purposes and commercial expediency. The Revenue cannot dictate a businessman's commercial decisions, but the assessee bears the onus to prove the business expediency.

A proviso inserted into a section to remedy unintended consequences, make the section workable, or supply an obvious omission must be read retrospectively in operation to give effect to the section as a whole.

Foreign exchange fluctuations, whether gains or losses, are inextricably linked to the underlying business transaction and must be accounted for under the mercantile system. The Supreme Court also affirmed the standard accounting principle of valuing stock at cost or net realisable value, whichever is lower.

A business liability that has definitely arisen in an accounting year is deductible even if it needs to be quantified and discharged later, as long as its incurring is certain and can be reasonably estimated.

A provision for expenses, such as warranty, is a deductible liability for income tax purposes if it constitutes a present obligation arising from past events, and a reliable estimate of the amount of obligation is possible.

For claiming deduction for bad debts under section 36(1)(vii) of the Income Tax Act, it is sufficient for the assessee to write off the debt as irrecoverable in its accounts, and it is not necessary to prove that the debt has actually become irrecoverable.

Tax must be deducted at source from payments made to a non-resident under Section 195 only if such payment is chargeable to tax in India. The Assessing Officer bears the onus to establish that the payments made are indeed chargeable to tax under the Income Tax Act.

Interest income earned on deposits, particularly before the commencement of business operations or as a requirement for business licensing, is taxable as "income from other sources" under Section 56, and cannot be treated as business income or set off against interest on borrowed funds.

The deductor cannot be treated as an assessee-in-default under Section 201(1) if the deductee has already paid the tax or offered the impugned receipts in their return of income. However, interest under Section 201(1A) for delayed deposit of tax can still be levied up to the date of filing of the return of income by the deductee.

When mixed funds are available, interest-free advances are presumed to be made from the assessee's own interest-free funds, preventing disallowance of interest expenditure under section 36(1)(iii). This principle also applies to section 14A disallowance, where interest expenditure is not disallowed if surplus funds are available and no direct nexus is established with borrowed funds for investments earning exempt income.