回複：請問有經驗的朋友,入籍可以提前多久申請呢?

If you submit your N-400 application more than 90 days of your 5th Green Card approval anniversary date. Your application will be returned because you're not qualified. However, you can save your time by preparing all the materials and send the application the day before the qualified date via Fedex overnight or something similar. Good luck,