Responsibility for mistakes at work

I work in an accounting firm. Sometimes it happens that there is a data-entry error or a lateness in submitting relevant client information to the agencies that collect the VAT or the income tax (because of pressure or because of human error). These errors entail fines. My question is: who is supposed to pay the fine, the client, the worker or the boss? I’d like to brings the following points to your attention: Sometimes the reason these mistakes are made is because a worker doesn’t know what she is supposed to do in certain situation. At other times, she makes a mistake because there is too much pressure on her from the excess of clients that she has to serve. We keep our clients’ checks or credit card information. We let the client know how much he has to pay (overall sum, without mentioning the fines), get his approval, and pay for him. The boss is of the opinion that we don’t have to let the client know that his monthly payment to the VAT or to the income tax agency includes a fine. I hope everything is clear. Thank you.  

It is the boss’s responsibility to pay the fine. It would be appropriate to let the client know that he’s paying one.

At any rate, this responsibility is not placed upon the workers. A worker is allowed to write a client receipt the way that the firm demands of her.