No you can pay tax even before filing your ITR but with a little bit of interest.
You can save tax in this scenario by either investing capital gain amount in another residential flat or by investing in bond's mentioned under section 54ec.
For investing in bonds you have 6 months and if you wish to buy residential flat within next 2 years invest the amount in capital gain account scheme of government and buy house within next 2 years.
You can't save tax by investing in commercial property or using spv.
If you need any further discussion you can try the phone consultation and I can even help you in filing your ITR.
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