Learn Farsi: قرار است که او یک نامه رسمی بنویسد. - He is supposed to write an official letter.

It follows the phrase قرار است که (it is planned that / is supposed to). Expressions showing expectation, intention, or obligation trigger the present subjunctive for the main action because that action hasn't actually happened yet—it is only a plan.

What does the word قرار literally mean in this phrase?

قرار by itself usually means arrangement, appointment, or agreement. So قرار است literally translates to "the arrangement is" or "it is established." When used with که and a subjunctive verb, it perfectly captures the English concept of being "supposed to" do something.

Can I move the subject او to the very beginning of the sentence?

Yes, you absolutely can. You could say او قرار است که یک نامه رسمی بنویسد. Even though قرار است is an impersonal phrase (literally "it is planned"), placing the logical subject at the start is very common in everyday Farsi and sounds just like "He is supposed to..." in English.

How do we connect نامه and رسمی when reading this sentence aloud?

You connect them using the ezafe vowel. Because نامه (letter) ends in a silent "h" that makes an "e" or "a" sound, you add a "ye" sound to link it to the adjective. It is pronounced nâmeh-ye rasmi. Notice that the number یک (a/one) sits before the noun and does not take an ezafe.

What is the present stem hidden inside the verb بنویسد?