AlanBarr:
So glad you mentioned that - one of the best films of all time in my opinion. I'm not sure about your "several opportunities" though, as Hayley Mills' character was quite a saint really. But certainly in that scene near the end where her husband gets angry and throws her down on the bed, a spanking could have been introduced very plausibly.
It's been a while, but:
When she drunkenly laughs at the bed collapsing.
There was at least once when each of her husband's parents seemed to be fed up with the situation.
When she visits her uncle (or was it her mother's cousin?) for advice, he could have told her to stop being silly, spanked her, and sent her home.
When the husband sought advice, the woman could have advised a spanking and offered to show him how to do it by spanking Hayley Mills' character in her office.
When her husband discovered that she had been going out dancing with her brother-in-law.
When she was (unwittingly?) teasing her brother-in-law in the bath tub scene.
Her parents could have done that (or advised it) when the parents got together and talked things out.
At the housing office when she revealed that she didn't have any children - the man behind the desk seemed very angry that they were wasting his time.
And the fight scene at the end, I would say it happened then, but the shouts stopped too abruptly.
But those are based on old memories - and perhaps wishful thinking.