When I was a nanny...100 years ago...LOL...my contract was written up to say I got a Cost of Living (COLA) raise each year on my Nanny-versary date, and a merit based raise at their discretion as well. There was also a minimum % written in for any subsequent children (they had one more).
It happened that my Nanny-versary date was my birthday..easy all around to remember...and my family was very generous. I always got the COLA, a decent percent merit raise....and religiously they gave me a 2 week (before taxes amount) cash envelope as a birthday gift. The last 3 of my 8 years with them I did not get the COLA raise, but still got the other things. We agreed to this due to me bringing my daughter with me each day from the time she was 18 days old.
But as I said....this was a long time ago (a little over 20 years ago)....and it was in my contract.