Hi there. You have identified a tricky area of law and the answer is not black and white. On the one hand, an employee owes their employer particular duties while they remain employed. This means an employee cannot use or disclose information that they have acquired through their employment if doing so would cause detriment to the employer. For example, using customer details for your own personal advantage while still employed would be a breach of your legal duties as an employee, even if you did not sign a written agreement with your employer.

However, once an employee has terminated their employment, they are generally allowed to use the knowledge and skill they have acquired during their employment for their own benefit, unless their employment contract prohibits them from doing so. This means a former employee may use their honestly acquired memory of the details of their former employer’s customers to generate business for their own personal benefit. In your situation, because you did not sign an employment contract or other agreement that referred to customer information, you may be legally allowed to contact your former employer’s customers for your own business.

That said, there is a fine line between information you have genuinely gained over the course of your employment, and going to the trouble of copying or recording customer information before you quit your job with the intention of using it to generate your own business. Your former employer may decide to commence legal proceedings against you if they believe you have breached a term of your employment (which may have been an implied term or part of an oral agreement, rather than a written contract), or otherwise breached your duty as an employee.