Yes, it is mandatory to give a paid holiday on polling day for Parliament and State Assembly.
Section 135B of the Representation of the People Act, 1951
1. Every person employed in any business, trade, industrial undertaking, or any other establishment and entitled to vote at an election to the House of the People or the Legislative Assembly of a State shall, on the day of the poll, be granted a holiday.
2. No deduction or abatement of the wages of any such person shall be made on account of a holiday having been granted in accordance with subsection (1). If such a person is employed on the basis that they would not ordinarily receive wages for such a day, they shall nonetheless be paid for such a day the wages they would have drawn had a holiday not been granted to them on that day.
3. If an employer contravenes the provisions of subsection (1) or subsection (2), then such an employer shall be punishable with a fine which may extend to five hundred rupees.
4. This section shall not apply to any elector whose absence may cause danger or substantial loss in respect of the employment in which they are engaged.
"Danger" or "substantial loss" is not defined anywhere.
Regards