我收到了一封来自税务部门关于我税款的来信。

I've had a letter from the tax authorities ___concerning my tax payments.

我写此信是为了回复您关于我获奖的来信。

I am writing in reply to your letter ___concerning the prize I won.

我们需要讨论关于项目截止日期的问题。

We need to discuss the issues ___concerning project deadlines.