If the employee has submitted letter of resignation then you cannot summarily turn it down just because he has put forth request to bring down notice period from 3 months to 15 days. You need to convey it to the employee to fulfil the conditions of employee as per the terms of appointment. Anyway following could be the draft of the letter:
Employee No ________
Acceptance of the Letter of Resignation1. Reference is made to your letter of resignation dated _______.
2. Under the provisions of clause No ______, paragraph No ______ of the appointment letter No __________ issued to you on _______ (date), notice period before quitting the employment is _____ months. However, in your letter of resignation, you have stated that you would like to separate from the company with 15 days notice.
3. Though your letter of resignation is accepted, the acceptance is subject to the fulfilment of the condition of notice period. Administration of _______ (name of your company) cannot accede to your requirement of reduction of notice period. You are hereby cautioned to complete notice period of three months and have a normal separation. Failure to complete the notice period will be considered as misconduct and appropriate disciplinary action could be initiated for this failure.
From India, Bangalore
The clause of the appointment letter as quoted below, may put the employer in considerable trouble as some employees may tend to misuse the provisions of 5 day absenteeism to get quick release from the service:
"If, for a period of 5 consecutive working days you are absent without sanction of leave or overstay, you shall lose your lien on your employment, and shall be deemed to have abandoned employment voluntarily."
I might have mis-interpret the clause as such practice is not common in Bangladesh.
Manager - HR