Using past tense to describe future events can be confusing and may not convey the intended meaning clearly. It is generally recommended to use future tense when referring to future events. In the example you provided, it would be clearer to say, "Hi, I would like to inform you that I won't be able to attend the lesson tomorrow because I am taking a day off from work." This sentence uses future tense ("won't be able to attend," "taking") to indicate a future event ("tomorrow").

That's fine, because you registered your day off at some point in the past, e.g. one week ago. Alternatively, without referring to that past 'booking', you could just say something like, "...I'm having a day off."

Vittorio, the tenses are correct grammatically. However, you may want to use the word 'booked'. It just makes it clearer as to the future sense of the action. 'Took' is definitely in the past and shouldn't be used here to refer to any future action. But 'booked' refers to an action done in the past that refers to whatever specified day in the present or future. I hope that helps.

Absolutely. Sometimes it cannot be avoided. For example, "I will not run in the race tomorrow because I broke my leg."

Thanks to all of you guys. I was figuring out if it was correct to use present simple for planned event (I can't attend.....) and past simple for something in the future, as I booked the day off tomorrow. Maybe it is correct, but I could have made less confusion re-wordering the sentence.