I pay 33% CGT of 33$ (so 39.6€)
If you did, you would have underpaid your CGT liability.
Your chargeable gain for CGT purposes is:
EUR value of the disposal proceeds of the Apple stock = EUR 1,320 (you use the FX rate on the day you sold the shares)
less
EUR value of the acquisition cost of the Apple stock = EUR 1,000 (you use the FX rate on the day you purchased the shares)
Chargeable Gain = EUR 320
CGT @ 33% (ignoring Annual Exemption) = EUR 105.60
This principle has been arrived at in case law and is legislated for in Section 552(1A):
Acquisition, enhancement and disposal costs.
www.charteredaccountants.ie
and Revenue guidance is outlined in paragraph 10.15 here:
You
don't convert the USD gain on the Apple stock into EUR at the FX rate on the date of disposal to calculate your CGT on the disposal of the Apple shares; you calculate it like I have outlined it above.
You had EUR 1,000 cash starting out. Cash is not a chargeable asset for CGT.
When you converted this into USD, you acquired foreign currency. Foreign currency is a chargeable asset (Asset A). See here:
When you used this USD cash to purchase Apple shares, you immediately disposed of the foreign currency asset (Asset A). No chargeable gain/loss arose as you acquired and disposed Asset A at the same exchange rate.
You now have a different chargeable asset - the Apple shares (Asset B).
Asset B went up in value and you decided to sell Asset B.
The lodging of the proceeds of the sale of the shares to your brokerage account resulted in the acquisition of a new asset - Asset A. A chargeable gain arose on the disposal of the shares and as paragraph 10.15 referenced to above makes clear, the consideration for the Apple shares is converted into the EUR value at the date of sale and the acquisition cost is the EUR value of the Apple shares on the day you bought them.
You decide to retain your holding in Asset A (the USD cash).
You are deemed to acquire this at the EUR/USD FX rate on the date you acquired this asset (the date you sold your Apple shares). USD strengthens against the EUR and so you have a MTM gain on this asset.
You decide to dispose of Asset A (the USD cash) and a chargeable gain will arise based on the principles outlined above.
I know that in your example you will be using funds in the brokerage account to pay your CGT bill on the disposal of the Apple shares (and not outside funds) but the principles outlined above still apply.