How Long Should Your 1-Month Notice Resignation Letter Be? Up to 150 words is good enough.Learn how to write a short notice resignation letter with this stepbystep guide, template and examples of formal resignation. Clearly state your intention to leave and when you will be leaving. While it is traditional to have a two week notice, it is possible to give more or less time. Here is a compilation of formal resignation letter templates to ease the pressure off you when writing your professional resignation letter. A resignation letter should be written at least 30 days prior to the effective date of resignation. Learn how to write a short notice resignation letter with samples. Find a solution to the challenge of resigning on short notice. Learn how to write a resignation letter with a notice period.