There comes a time in any working professional's life when he or she decides to leave for greener employment pastures, but has one last all-important task left before heading out the door.

Writing a resignation letter.

Career professionals who don't write a proper resignation letter risk making a classic career blunder - burning a bridge with an employer who may be in a position to aid you later on, when there was no reason to do so.

Formally signaling your decision to leave an employer is a sign that you're an employee leaving in good stead, are leaving doors open for future relationships with your current company and its employees, and allows you to leave a position on your terms, and in an efficient and respectful manner.

In a recent survey of 600 human resources managers by Robert Half, 86% of HR managers say the way you leave a post can negatively impact your career path and limit future quality job opportunities.

The fact is, leaving a job in bad terms, as more millennials are doing by "ghosting" employers (leaving without so much as a call, email or even text) is a toxic career move. Instead, take the wise road and leave a job in good graces. A solid resignation letter can do the job for you - if you know how to craft that letter correctly.

Two Reasons to Write a Resignation Letter

Aside from doing the right thing and giving your employer a helpful "heads-up" that you're leaving, a resignation note can offer the writer the following benefits:

1. It's Cathartic

Putting an official end to your tenure at your old job provides a sense of closure, and gives you peace of mind as you move on to a new opportunity.

2. It May Help Down the Road

A resignation letter will likely be appreciated by your current employer and that might come in handy down the road if you need a professional reference for another position - or if you want your old job back.

It stamps you as a career professional who'll do the right thing. You're likely never around when your name comes up in a professional setting, like when promotions and bonuses are given out, or if you're up for a new job.

Having written a sincere and professional resignation letter may have gotten noticed, and when your name comes up, it will come up in a complementary manner.

Three Reasons Not to Write a Resignation Letter

There are several reasons not to write a resignation letter - and they're on target and may even save your career.

1. It Could Come Back to Bite You

If you're embroiled in a combative departure from a company, and legal implications are hovering over the scene, a resignation letter - especially a heated one written in the throes of emotion - can be used as evidence against you in any legal scenario.

2. When You've Agreed Verbally to Accept a New Job 

If you haven't gotten a new job offer in writing, with the conditions you've agreed upon, hold off on any talk or documentation of leaving your current post until you do get the new offer in writing.

Once a resignation letter is submitted, it's tough to take that departure notice back.

3. When Your Company has Another Form of Departure Notification

Some companies march to their own beat, and say that a resignation letter isn't necessary. A verbal declaration and possibly an exit interview works for them.

How To Write a Resignation Letter

When it comes right down to it, crafting a great resignation letter is a matter of "do's" and "don'ts."

In other words, knowing what to do and what not to do can easily spell the difference between a masterful resignation letter and one that looks like you wrote it when you got home from happy hour.

Let's take a look and what to - and what not to do - with a resignation letter.

1. Personalize It With the Manager's Name

Address the letter to your immediate supervisor - he or she knows you best and will forward the note up the chain of command - the way senior management likes it. Avoid wooden terms like "to whom it may concern" and instead go with "Dear ____ (insert name)" to start your letter.

TheStreet Recommends

2. Get the Basics Right

Remember, this is a business letter and function is a priority. Make sure to date your letter, include your name and title, and your address and contact information at the top of the document.

In addressing your manager do so at the upper left-hand side of the letter, below your name and contact information.

In the lead sentence of your resignation letter, make it clear that you are signaling your official intent to leave the company and should include a negotiable departure date, with two weeks being a good frame of reference from the date of your resignation letter.

3. Express Gratitude

In the paragraph below your lead sentence, make sure to express your gratitude for the opportunity to work at the firm you're leaving.

Feel free to include a line or two on what you learned, how you've applied it to your career, and a specific highlight of your time on the job. Also, if appropriate to your situation, thank your manager for his or her role in shaping your career arc and note their professionalism in your day-to-day interactions.

4. Offer to Train Your Replacement

As a last statement of goodwill, offer to provide your skill and expertise to train your successor. Your employer may or may not take you up on the offer, but your manager will appreciate the gesture and will likely file your kind offer away for future reference.

5. Do Ask for a Future Reference

Human resources professionals seem divided on this issue but there's really no reason not ask your manager for a direct professional reference, if needed, down the road. If you've been a model employee, your employer will be glad to provide both a character and professional reference, when and if needed.

6. Sign Off With a Positive Attitude

Finish your letter with genuine well wishes for the manager and your company, and offer to answer any questions, or signal your acceptance for an exit interview. This will instill you as a team player in your employer's eyes, and help keep relations open in the future.

7. End Your Resignation Letter With Your Signature

Your last entry in your resignation letter is easy-peasy - just include the term "sincerely" or "best regards" on the lower left side of the page, with your signature directly below. Type your name right below your signature for added clarity.

What Not to Do With a Resignation Letter

Many a resignation letter is weakened, if not ruined outright, by these mistakes..

1. Don't Go Negative

The absolute worst move you can make with a resignation letter is to use it as a platform to air grievances. Tempted by the freedom associated with leaving a job once and for all, some resignation letter writers go low when they should be focused on going high.

Issuing opinions on managers and staffers, calling out lower pay (even if justified), or bemoaning the lack of good benefits are all messages you just can't include in a resignation letter.

Always keep the letter positive and restrict the venting for your friends or spouse. If you feel compelled to make a complaint or offer a negative opinion, do so in the job exit interview and express your thoughts diplomatically.

2. Don't Go the Digital Route

Avoiding writing and transmitting your resignation letter via email or worse, by text. The human touch is still highly appreciated (and recommended) with an employment departure note.

By all means, write your letter via computer or laptop, print it out and deliver it to your manager in person. Your professionalism will be highlighted and you'll walk away from the experience knowing you did the right thing, and the right away.

3. Don't Neglect the 2-Week Departure Offer

Leaving your firm, even if you do write a resignation letter, without offering a 2-week departure notice is leaving the firm in bad form.

Think of it this way - you've come this far on the job and have gone to the length of writing a solid resignation letter. Why would you toss those good vibes aside by declining to offer a 2-week notice?

A Savvy Career Move - and the Right Career Move to Make

While there are components of a resignation letter that are necessary and productive - think of a sense of gratitude and a round of best wishes on your way out the door - a resignation note really is a letter of function.

Writing one properly declares your decision to move on from a company and will be shared with your manager, the human resources department, and depending on the situation, senior management as well.

Hey, you might even decide to share your resignation letter (or write a new one) with your co-workers, as a sign of good faith and team play.

No matter what, when you can strike a balance of the personal and the (career) political in your departure note, you are sending the message that needs to be sent, so you can move on to new opportunities and to greater heights.