邀请信是在形式上不如请柬那样正规，但也是很考究。形式上大体分为两种:一种为正规的格式 (formalcorrespondence)，亦称请柬;一种是非正式格式 (informal correspondence), 即一般的邀请信。
　　书写时应注意:
　　邀请信一定要将邀请的时间(年、月、日、钟点)、地点、场合写清楚，不能使接信人存在任何疑虑。 　　例如:“I’d like you and Bob to come to Luncheon next Friday.”
　　这句话中所指的是哪个星期五并不明确，所以应加上具体日期, “I’d like you and Bob to come to luncheon nextFriday, May the fifth.”
　　邀请朋友共进午餐 Inviting a friend to informal luncheon
　　Dear [Zhang Ying]:
　　Will you come to luncheon on [Friday, May the fifth], at [twelveo’clock]?
　　My niece [Mary] is visiting us and I think you will enjoy meeting her. Sheis a charming, very pretty girl … and very good company! [John and Jane] will behere, and perhaps we can [give a dance] after luncheon. Do say you’ll come!
　　Affectionately yours,
　　Li Ming
　　亲爱的[张营]:
　　您能在[5月5日星期五中午12点钟] 来吃午饭吗?
　　我侄女[玛丽]正在我们家中作客，我想您会乐于见到她的。她是个漂亮而聪明的女孩子，……同她在一起是很使人高兴的![约翰和简]也到这里来，也许在饭后我们能[开个舞会]，说好，一定得来呀!