Under common law there is a doctrine of agency. As it applies in the employer/employee relationship, it holds that an employee, while acting in the scope of his or her duties is acting as an agent for the employer. In that way the employer is liable for the actins of his agent and the agent is not liable. (Note the disclaimer within the scope of duties. If you are outside the scope of duties then you are most likely on your own.)
The reasoning is that the employee is acting as an extension of the employer and under the employer’s direction and control. Therefore the agent is not liable but the liability falls back to the principal. If the employer is a limited company, the company has the liability not any individual person. (A limited company is a legal fictional person with all the rights and liabilities of a person in contract and tort.)
Your locality jurisdiction may have modified this general rule of agency and it would be a good idea to get legal advice if this is other that idle curiosity causing the question. If you are engaged as other that a pay rolled employee, i.e. contract or other arrangement, then you may not be the agent but an arms length contractor. In this case the client would be able to sue you or any losses suffered as a result of your actions.
Professional liability is different than personal liability. If you are a P.Eng or equal, then your local association will have the responsibility to take action against you professionally. This could mean placing restrictions on your ability to practice up to and including permanent expulsion from the profession and or administrative fines and other penalties. I do not believe that they could order you to pay damages and restitution out of your own pocket.
Once again, I caution you that if this question is other than simple curiosity, get competent legal advice on your specific circumstances. I’m not a lawyer and the above is simply my understanding of common law.
Rick Kitson MBA P.Eng
Construction Project Management
From conception to completion