It is a good idea to write it, that way there are no discrepencies and there is a record. Be sure to put the date on it, your full name, your last date of employment, and your reason for quitting. Keep it short. A good example is:
To whom it may concern, May 20, 2008
This letter is to serve as my two weeks notice. I have gained a better position with another store closer to home, and I have decided to continue in that position.
My last date of work will be Tuesday, June, 3.
I appreciate the time that I have spent with this company and the opportunities that you have given me.
-Susie McSuserson
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So when you're happy (Hurray!), or sad (Aw!),
Or frightened (Eeek!), or mad (Rats!)
An interjection starts a sentence right.