Q: My father isn't practising and has never paid Zakat up to this date. Can I pay Zakat on his behalf?

A: The Zakat paid on behalf of a sane adult will not be valid if it has been paid without their permission.
For the Zakat to be valid, there must be an intention from the payer which clearly isn't the case in your situation unless you seek your father's permission.
There is no disagreement on this issue between any of the 4 schools of jurisprudence.

See the link below:

Having the "intention" (niyyat) when giving Zakat

And Allah knows best!

Mufti Billal Omarjee