Minor error requires my correction

I made a minor error on the year of a document that I was notarizing. Now I need to return to correct it before it can be filed necessitating an extra trip for my client to the county offices. What is the best way to express my regret for the error? Obviously I will not be charging to return to correct it but I feel like offering to take it to the county offices for them to file to save them trip. Would that be appropriate and enough? How would you handle this to retain your reputation and hopefully make the client satisfied?