Business letters

Hi.. Am finding it hard to write business letters and memo. My senior told me that when I write letters to clients, I write as If I am talking to them and its not the correct method!
Could someone help me with this pleaseeee...

For eg: We had a meeting 2 days ago and there came up an issue that the employees hav'nt got their medical cards yet. So my department wants me to write a memo to all employees that as per the meeting, they have to go and get their Govt. medical card from the hospital and this is a basic rule of the company. How can I write this as a memo.

Please Help!!!

Thanks,

[oregeezer]

I am an American native speaker with about 75 years of speaking English. I have been told that the best writing is just like talking!
Memo-speak:
All employees must report to the hospital to pick up their medical cards before the
15th of the month. This rule must be observed by all current and future employees.