Addresses, dates, and times are typically spelled out. A formal invitation card should use third person (e.g., they, their) rather than first (e.g., I, we, my, our) and include the full names of the event's hosts. Letters may use first person, typically we, but should still maintain a formal tone.
How do you invite a couple for dinner?
Include the date, time, and address of the party.
Specify the dress code for the event.
Tell the recipient's what the occasion is for.
Do you expect donations or don't want anyone to bring gifts?
Give them a contact and deadline to send in RSVP's.
Formal Invitation is a letter, written in formal language, in the stipulated format for official purpose. While, Informal letter is a letter written in an friendly manner to someone you are familiar with.
Call, email or invite people in person to come to your home for a meal. If the meal is a formal affair, hand out or mail written invitations. Use pre-printed, formal invitations with an enclosed reply card for a formal meal.