RBI faq states redemption with RBI is tax free.
RBI redemption happens on maturity or else when they ask if you want to sell after 5 years. First part is tax free, second part is how you interpret the FAQ.
This was discussed here
It is bit grey out here. I think law only says that capital gains is tax free if SGB is held till maturity.
It does not differentiate if SGB were bought in primary market or secondary market.
This should not be a concern because whatever you held till maturity will be tax free.
In your ex, you bought 10 in primary market and 5 from secondary (but that difference is immaterial).
So if you held all 15 till maturity, CG for all 15 will be tax free
if you sold 5 in between and held 10 till ma…
and in some other threads as well