new delhi, Feb. 10 -- A Union budget effort to march corporates into India's new low-tax regime may deal a one-time blow to several companies following the old tax regime. Restrictions on tax credits under minimum alternate tax (MAT) may force startups and power sector firms to shift to the new regime, or contend with the higher cost of staying in the old regime, experts said. Under the old tax regime, companies are required to pay minimum alternate tax (MAT) at 15% of book profits when their tax liability, after claiming deductions, falls below the MAT level. If their taxable income after accounting for exemptions is below 15%, they must still pay MAT at 15%, but they get back the difference as credits-called deferred tax asset in accounti...