Dear :

Thank you for inviting me to speak at [seminar/meeting]. I am delighted to have an opportunity to speak to such a distinguished audience.

I understand my speech will be at [time] on [date] and the topic will be "." I will speak for minutes and then answer questions from the audience. There will also be handouts and slides to highlight the major points.

I look forward to seeing you at the seminar! Thanks again for your invitation.

Yours sincerely,

[name]

[title]