NEW DELHI: Uncertainty over the date of the goods and sevices tax ( GST ) rollout is posing a dilemma for finance mandarins as they finalise this year’s budget.The original expectation was that the budget would not touch upon excise duties and service tax as they would be rolled into the multiple-rates GST structure, which was to come into being from April 1, 2017.But with hopes of meeting the April 1 deadline receding, the government will have to quickly take a call on whether it will rejig indirect taxes in the budget to prepare for the launch of GST or leave them as they are till the new regime comes into force.The final decision could have ramifications on revenue estimates and collections for the next fiscal year as well as the levies imposed on different products and services. According to the GST constitutional amendment passed by Parliament last year, the current indirect tax regime will lapse by September 17.“We will take a call next week,” said a senior government official privy to the deliberations on the matter. In addition to the rates, the government will also have to decide whether it wants to continue with the current method of presenting separate estimates for excise duties, customs duty and service tax. Tax experts say lack of clarity over the rollout date for the GST regime presents a problem for the government.“The budget is a challenge as neither the date nor the rates (which products would get classified in which bracket) are likely to be finalised by February 1. Further, the breakup of CGST and SGST still needs to be agreed between the Centre and states,” says Pratik Jain, leader, indirect taxes, PwC.Most government officials said it is unlikely that indirect tax rates would be changed, but it is possible that exemptions and other distortions in the indirect tax structure could be removed. The government could attempt at rationalising the structure in line with the proposed GST framework but rates may be left unchanged,” said one official.One of the options is to go ahead with the taxation regime that is in force as of now and prepare estimates on the basis of current taxes. “Revenues can be presented as it is with current taxes and a foot note on GST…Changes can be made when the revised estimates are presented,” said a second government official.PwC’s Jain says the government would have to work with certain set of assumptions and possibly create some kind of contingency fund, should these assumptions don't work out. Buffer so created would make up for any shortfall that may arise due to any delay in implementation of the GST and difference between tax rates now and proposed under GST. The loose ends on the GST front that have not been tied up yet are also complicating matters for the government.GST is planned as a revenue-neutral exercise, which means that the switchover to new regime should not impact overall tax revenues of the government, but some cushion will have to be provided for taking into account the uncertainties around the new tax structure.The GST Council has finalised the tax rate structure, but what goods will fit in which slab and what will be the tax on services is still being worked out. States have also sought higher proportion of the revenues than 50%, which also lends an element of uncertainty to the ongoing budget process. In addition, excise exempt items as of now exceed those exempted under the proposed value added tax. A large number of services, which could also come under the ambit of GST, too are currently tax free.