Breakdown of Deve scriverlo subito, altrimenti il cliente non accetterà il riepilogo.
non
not
scrivere
to write
subito
immediately / right away
dovere
must
Questions & Answers about Deve scriverlo subito, altrimenti il cliente non accetterà il riepilogo.
Does altrimenti require the subjunctive mood to express a condition?
No, it doesn't. altrimenti (meaning "otherwise" or "if not") acts as a coordinating conjunction introducing a factual consequence, so it pairs with the indicative mood. That's why the sentence uses the future indicative accetterà instead of a subjunctive form. This makes it much simpler to use than conditional connectors like a patto che (provided that), which do require the subjunctive.
Is it mandatory to use the future tense (accetterà) after altrimenti?
Not always, but it is the most natural choice here for expressing a definite future consequence of a present action: "Do this now, otherwise [this will happen later]." You could also use the conditional mood (e.g., altrimenti il cliente non accetterebbe... - "otherwise the client wouldn't accept...") if you wanted to frame the consequence as a hypothetical scenario rather than a certainty.
How do we know deve means "you must" here instead of "he/she must"?
Out of context, deve can indeed mean "he must" or "she must." However, translating it as "you must" reveals it is being used as the formal Lei (formal "you"), which always takes third-person verb conjugations. This formal tone makes sense in a business context with a cliente (client). If you were speaking informally, you would say devi scriverlo.
Quick refresher: could I put the pronoun lo before the verb instead of attaching it to scrivere?