How Important Is a Resignation Letter in How To Quit A Job?

[TechCounselling]

When learning How To Quit A Job, I noticed that writing a resignation letter is often recommended even if you have already told your manager verbally. I’m unsure how detailed it should be and whether it should include reasons for leaving or just basic information like the last working day. What has been your experience with resignation letters? Do companies still consider them important today, and what is the best way to keep them professional, short, and effective?