In new regime, people will have more income at their disposal so overall expenditure in economy will increase which will accelerate GDP must faster than saving.
For example, my salary is Rs. 8 lakh. In old regime, my tax would be Rs. 65000 (20% on 2.5 lakhs and 5% on 2.5 lakhs plus 3%) without exemption. Now in order to claim deduction under Section 80C suppose I invested Rs. 1.5 lakhs in ELSS Mutual funds. Now my tax will drop to Rs. 33000. However, my net disposable income will be around Rs. 5.5-5.7 lakhs and my Rs. 1.5 lakh will be locked down for 3 years.
In new scheme, my tax will be Rs. 41000. My net disposable income will be Rs. 7-7.2 lakhs which I can use on my own discretion. I can invest it in Debt Mutual Funds which are less risky than ELSS MF which we can't do same in old degime as debt funds aren't available for deduction u/s 80C.
Hope things are more clear to you all. However, even I feel budget wasn't up to expectations. I was expecting more perks for industrial sector but government only gave tax benefits to new manufacturing businesses and startups. Nothing revolutionary in budget.
In your salary part there is 100 perks that is exempted under old regime and in new regime 70/100 taxable like HRA, other thing ELSS earning is tax free and debt investment will be taxable, so calculate everything before thinking that new tax regime is good.
In your 8 Lakhs income if you use all perks and tax saving instruments, your tax will be around 10-20k max. If you are not using that talk to your HR, he/she will be help you to save tax to redesign your CTC.
In India there is nothing post retirement from govt, if Govt discourage people from investing it will hurt mostly Indian after retirement because If they don't invest for their retirement god knows, how they will survive after retirement.
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It's not public responsibilities to increase GDP by reduce investment/saving and spending more, it's govt. responsibility to attract more investment and build more factories and businesses so they will create more jobs so more people will have earning and so they will able to spend freely.