"I have neither."
Translation:Níl ceachtar agam.
tá X agam - "I have X"
níl X agam - "I don't have X"
níl ceachtar agam - "I don't have either"/"I have neither".
To translate "Neither have I" depends on what you are referring to. To agree or disagree with something in Irish, you repeat the verb:
"I haven't seen it". "Neither have I" (I haven't seen it either)
Ní fhaca mé é. Ní fhaca mé é ach an oiread
"I haven't heard of it". "Neither have I" (I haven't heard of it either)
Níor chuala mé faoi. Níor chuala mé faoi ach an oiread