Tax on a deceased's Retirement Annuity

I received money from my late dad's Retirement Annuity and I was taxed on this. Does that
matter at all?

You should declare it on your tax return under the none taxable income section and list it as an inheritance.
The Retirement Annuity should've been included in your father's deceased estate and would have already been taxed there so you wont be taxed on it again.