Dear Ms. Anderson,
Following our conversation earlier this week I regret to inform you that your services with the Company will not be required with effect from 31 July 2xxx.
As you know there have been a number of occasions recently when I have had to point out the unsatisfactory quality of your work. Together with your persistent unpunctually in spite of several warnings, this has led me to believe that you will perhaps be more successful in a different kind of work.
I hope you will be successful in finding suitable employment elsewhere. If another employer should wish you to start work before the end of the month, arrangements can be made for you to be released immediately.