(idiomatic,Britain,Ireland,Australia,New Zealand) Said on the first day of a new month, accompanied by a pinch and a punch to the victim, by way of a prank. The victim can then say 'A slap and a kick for being so quick!' accompanied with said flick and kick. This can then be followed with 'A punch in the eye, for being so sly' accompanied with a hit to the face.
2009, Ellie Nielsen, Buying a Piece of Paris: A Memoir, page 208:
‘Pinch and a punch for the first of the month.’ I nurse my wounded arm and look down at my giggling son.
'You just hit me.'
'No I didn't. That's what you do on the first of the month.'
(quotations which support a broader or different sense):
2007, Anne Barry, Playing with Fire, page 59:
Bugger, this wasn't the goods at all – this was a pinch and a punch for the first of the month. A letter in fact from Fire Commander Bruce stating that although he was in receipt of my application, neither he nor the Fire Commander of IB were certain of the Fire Service Commission's final policy for employment of women as operational firemen.