Taking the piss

phr.

Heard in Dublin and Armagh

Teasing, mocking, or joking with someone in a mischievous manner.

In use

Ah your taking the piss now, there's no way that horse won the grand national!

Posh English

You are unquestionably jesting with me now, for there is no conceivable possibility that equine animal triumphed in the race!

Same phrase, other counties