Please undergo a medical check-up. / You are required to undergo an annual medical check-up.
I/We are contacting you because you still have not undergone your annual medical check-up.
It is company policy that all employees undergo medical check-ups once a year.
「[健康診断](https://eikaiwa.dmm.com/uknow/questions/38168/)を受けて下さい」＝ Please undergo a medical check-up. / You are required to undergo an annual medical check-up.
「今年度の健康診断が未受診だったため、[ご連絡](https://eikaiwa.dmm.com/uknow/questions/32892/)しました。」＝ I/We are contacting you because you still have not undergone your annual medical check-up.
「年に一回の健康診断は会社の決まりです。」＝ It is company policy that all employees undergo medical check-ups once a year.
「また、ご自身の健康を確認するためにも、必ず健康診断を受けましょう。」＝ Medical check-ups are important as they allow us to check the state of our health, prevent any future health problems, and treat problems before they get worse. （これは直訳ではありませんが、健康診断の重要さをはっきり説明しています）
「-ご希望の日にちをお知らせください。」＝ Please contact me as soon as possible to let me know your preferred dates for your health check-up.
Please make an appointment for your annual checkup
Please have your annual checkup
[健康診断](https://eikaiwa.dmm.com/uknow/questions/38168/)は英語でcheckupと言います。年度の健康診断はannual checkupといいます。
挙げて頂いた例文ですと
-[今年度](https://eikaiwa.dmm.com/uknow/questions/31133/)の健康診断が未受診だったため、ご連絡しました。
You are being contacted because you have not yet had your annual checkup.
-年に一回の健康診断は会社の決まりです。
Company requirements state that all employees much undergo an annual checkup
-また、ご自身の健康を確認するためにも、必ず健康診断を受けましょう。
Having an annual checkup is also for your own personal benefit.
-ご希望の日にちをお知らせください。
Please inform us as to which dates you would be available to have a checkup
が一つの言い方になります。
この説明が役に立つと嬉しいです。
イギリス 
アメリカ合衆国 
