Invitation letter to a person

[Bracks_29@yahoo.com]

im just asking what would be the precise format of a formal letter when you are inviting a person on a seminar as speaker.plzzzzzzzzzzzz help me for this problem.

[English-coach]

Dear ***,

I am pleased to invite you to____________________ (provide function name, date, time and location).

Include any other useful information (dress code, hotel info, what materials should be brought or will be provided).

Request their RSVP (tell you if they are going to attend or not).

I look forward to hearing from you etc etc

Sincerly________________

That is a basic outline of an invite. (it might not be formal enough...but Anglika suggests a more formal option below)
http://www.helping-you-learn-english.com

[Anglika]

A formal invitation:

XXXXX has much pleasure in inviting YYYYY to attend [title of event], at [name of location] on [date] at [time].

RSVP
[name and address to which this is to be sent:
XXXXX
address line 1
address line 2
address line 3]