If you're a company or individual providing professional advice or services you can be held liable for financial loss of a client arising from errors or omissions committed by themselves or their employees
Professionals are only human and sometimes make mistakes. Such as loss of client documentation, failure to advise client, acting without proper instructions from client, wrongful or inadequate instructions to client.
This is where Professional Indemnity cover will give you peace of mind when providing advice to your clients. If you charge a fee for your advice, service or design you should consider this cover.