Thanks, i should have mentioned assuming the 1270 has been exceeded..Yes, but no.
You bought 50 shares at €20 a pop.
You’re selling 25 shares at €40 a pop for €1,000.
So the base cost for those 25 shares is €500.
That’s a €500 gain.
But it’s below the €1,270 Personal Exemption, so no CGT.