Falling asleep in a cupboard is fine, as is drunkenly asking for a pay rise or promotion, but there are some lines that if you cross you could be out on your ear faster than you can say Jeremy Clarkson.
That's thanks to two words that are in almost everyone's employment contract: Gross misconduct.
Fall foul of this and you can be marched out the door without notice or compensation.
Worse, you can be sacked for gross misconduct even when you're not at work - if you're in what's called a "work context" - such as, say, the office Christmas party.
"The work Christmas party should be considered to be an extension of the workplace, so the same rules will apply," explained Louise Newbould-Walton, associate solicitor at DAS Law.
"At an office party however, the professional line is often blurred, usually fuelled by alcohol which might even have been provided by the employer."
So, can your boss just sack you then?
Most of the time you have rights to stop you from being sacked on the spot - as employment contracts cut both ways.
But cross the line on something that can be considered 'gross misconduct' and that contract goes out the window.
"Generally speaking, an act of gross misconduct is potentially serious enough to fundamentally breach the contract between employer and employee, and justify summary dismissal," Newbould-Walton said.
"Common examples of Christmas party gross misconduct are serious insubordination, harassment, and damage to company property.
"This list is not exhaustive and if there is an incident which is sufficiently closely connected to work, and will likely impact on the working situation, then it is likely that the employer will be able to start a disciplinary investigation regarding the matter."
What counts as gross misconduct?
Gross misconduct varies from firm to firm, but there are a series of offences that almost always count.
These are:
Physical violence or bullying - drink is no excuse for punching Mike from accounts
Theft - this speaks for itself, but it's not a good idea to be caught sneaking the work TV out because yours is broken
Unlawful discrimination or harassment - No, mistletoe is not an excuse for ignoring the normal rules around what is or isn't acceptable behaviour with your colleagues
Causing loss or damage through negligence - for example leaving the office party drunk and forgetting to lock up
Serious health and safety violations - it might seem like a great idea to try out knife-throwing skills learnt on YouTube by putting an apple on Janet from HR's head, but imagine the paperwork if you tried to do it in the office normally
Serious incapacity at work due to alcohol or drugs - for example coming into work drunk from the night before, especially if your job required you to drive or operate machinery
There's a full list of the 12 factors on page 31 of this document.
But I'm not in work!
You can be fired for committing an act of gross misconduct even if you're not at work, but there are conditions.
Philip Pepper, partner at law firm Shakespeare Martineau, said: "It has to be within a work context."
Offences outside work contexts can count too, if there are "legitimate implications for the business".
Pepper gave the example of someone getting into a fight while wearing work uniform, that was captured on CCTV and shown on the news.
However, if you're watching the football in a pub on the weekend, and are involved in a "fracas" with a colleague, that would not count as grounds for dismissal, Pepper added, although bosses would be wise to try and ensure it did not have a knock on effect at work.
Is that it then?
Not quite. Your employer needs evidence to support the fact you've been found guilty of gross misconduct before they can turf you out.
They also need to take any mitigating circumstances into account and generally look at length of service too.
More than that, they have to follow a fair process in deciding to let you go, or you could have grounds for appeal.
If you do appeal, the authorities will look at the process by which your bosses arrived at the decision to let you go. For example, did they conduct a thorough investigation and speak to the relevant witnesses?
There might also be grounds for appeal if you've been sacked for something that many other people haven't been sacked for, despite the management knowing about it.
