Do I use last or first name?

[robin lee]

I am writing a letter of resignation to my manager. I am not sure if I should use her first name or last name in the salutation as I know her.


XYZ Company
Attention: Mary Smith, Manager

Dear Ms. Smith:

Further to our meeting last Tuesday, I confirm I will be resigning from my job effective November 25, 2017

or

XYZ Company
Attention: Mary Smith, Manager

Dear Mary:
Further to our meeting last Tuesday, I confirm I will be resigning from my job effective November 25, 2017

 

[emsr2d2]

It's an official notification of resignation so I would be as formal as possible. Start with "Dear Ms Smith" and end with "Yours sincerely" (then your name).

We don't usually say "I will be resigning from my job effective from ...". It's more normal to say something like "Please accept this letter as official notice of my resignation. In line with company policy, I am giving the requisite (number) weeks' notice so my last day will be [date]."