The main reason to register a company is that it is a separate legal person: its debts are its own, and they stop at the company. That protection is real, and it is narrower than most owners believe.
Here are the ways it does not hold.
Personal surety
The most common by a very long way, and the most voluntary. A landlord, a bank, a vehicle financier or a large supplier asks a director to sign personally alongside the company, precisely because they know what limited liability means.
Once signed, that debt is yours. Closing the company does not touch it. It simply removes the entity that stood between the creditor and you.
Read what you sign, know which sureties exist, and keep a list. A surprising number of owners cannot say with confidence which of their company's obligations they have personally guaranteed, and that is exactly the thing to know before a difficult decision, not after.
Money withheld on somebody else's behalf
Employees' tax, UIF and similar deductions are not the company's money — they were withheld from someone's pay to be handed on. Failing to pay them over can reach directors personally, and it is treated much more seriously than an ordinary trading debt.
When cash is tight this is the tempting balance sitting in the account. It is the one thing not to touch.
Trading while unable to pay
Directors have duties, and continuing to incur debt on behalf of a company you know cannot meet it is where reckless trading arises. The consequence can be personal liability for those debts.
The difficulty in practice is that the point of no return is only obvious afterwards. That is precisely why taking advice early matters — an owner who documented that they took advice, considered the options and acted on them is in a very different position from one who hoped and kept ordering stock.
Not keeping the company separate
Running personal expenses through the company account, mixing funds, using company assets as your own, not keeping records — none of this is fatal on its own, but it undermines the argument that the company was ever genuinely a separate thing.
The separation is something you maintain, not something you registered once.
Specific statutory duties
Various obligations attach to directors personally rather than to the company: certain health and safety duties, certain environmental ones, and the accuracy of what you certify to regulators. Signing something on behalf of the company that you know to be untrue is a personal act.
What actually protects you
Keeping the company's affairs separate and documented. Not signing personal surety where you can avoid it, and knowing where you could not. Paying over withheld money first, always. Taking advice early when the business is in difficulty, and being able to show you did. And carrying appropriate insurance, including cover for directors where the exposure warrants it.
None of that is exotic. It is mostly bookkeeping and paying attention, which is a reassuring answer and an easy one to postpone.
General guidance, not legal advice. Directors' duties and personal liability are fact-specific and consequential; take proper advice on your own circumstances.