I am not sure how to calculate any gains on the fund
The tax treatment of these funds is contained in the prospectus which is at the bottom of the page linked to above.
It looks like exit tax @ 41% is payable on fund gains.
Definitely check your documentation/correspondence that no tax has been deducted at source at the time of encashment or at any time prior.
You had a partial encashment for €30,000.
Check what the value of the fund was before this partial encashment - let's say €100,000 for the sake of example.
As far as my understanding/experience goes of partial encashments of funds, and I'm not a financial adviser or tax adviser, the gain on the partial encashment is:
€30,000 - €80,000 x [€30,000 / €100,000] = €30,000 - €24,000 = €6,000
Exit tax of 41% on €6,000 is due = €2,460
I do my own tax online with the form 11 but I am unsure where on the form do I put any tax gained from this fund?
The footnote on page 9 of the Revenue Guidance on Investment Undertakings is:
"where....exit tax has not been applied to the payment, the payment is treated as if it is a payment from an offshore fund to which the provisions of Chapter 4 apply. Section 747D provides for payments in respect of offshore funds and Section 747E provides for disposals of an interest in offshore funds."
In that event, insert the gain in the "Gain taxable at 41% (S.747E(1)(b)(ii)" box in Form 11 in the 'Offshore Funds' section of the form.
I'm sure your account/relationship manager in Goodbody can hopefully give you a steer on the above. They should have private client tax experts available to you for the fees you are paying them on the fund.