Many parents have often been faced with this dilemma - their child is being exceptionally naughty and stern words and threats don't seem to be doing the trick.
Smacking is considered by many parents and most child behavioural experts to be an inappropriate punishment.
It is, in fact, illegal in England - but parents and guardians have a defence under the Children Act 2004.
They can under prosecution claim a defence that the smack was 'reasonable punishment'. This no excessive force may be used and no physical harm may come to the child that is covered by legislation governing criminal assaults, e.g. actual or grievous bodily harm.
But there could be a change coming in Scotland and Wales which could land you in bother if you physically discipline your son or daughter there.
Smacking is currently legal in Wales and Scotland but the countries respective assemblies are planning to outlaw it.
According to Wales Online , the country will remove the legal defence that currently protects parents - the same stance Scotland announced last month.
That will leave England as the only place where parents are legally still allowed to smack their children but could cause problems for any English parents taking their children over the borders.
So what is the current law?
According to charity Child Law Advice, smacking is illegal here in England, but has a legal defence of "reasonable punishment" under section 58 of the Children Act 2004. This only applies to parents and legal guardians.
But what that is defined as is not set out in law so is a grey area and depends on each individual case.
Factors such as the age of the child and the nature of the strike are considerations.
But it is illegal for teachers, nursery staff, care workers to smack children. Privately-hired carers such as nannies or babysitters may smack, but only if permission has been given by the parents.
Smacking a child becomes illegal when it is seen as an offence under other legislation - such as wounding, actual bodily harm, grievous bodily harm or child cruelty.
For example this could be leaving marks on a child or using an implement such as a cane or belt.
The NSPCC has approved of the Welsh Assembly's proposals, saying: “Every child deserves equal protection under the law and should be protected from such draconian forms of discipline.
"It is wrong that a defence which does not exist in a case of common assault against an adult can be used to justify striking a child."
Anyone who is concerned about a child should contact them on 0808 800 5000.