An ordinary German conditional clause begins with the connector wenn, but in formal, literary, and journalistic register, wenn can be dropped altogether and the condition expressed through a single syntactic move: fronting the conjugated verb to the very start of the clause, exactly as happens in yes/no questions. So instead of Wenn du Zeit hast, komm vorbei, the sentence becomes Hast du Zeit, komm vorbei. This construction changes nothing about the meaning; it simply raises the level of formality and stylistic polish, and it is one of the hallmarks of advanced written style.
The mechanism relies entirely on word order rather than on any new connector: since wenn, as a subordinating conjunction, is what pushes the verb to the end of the subordinate clause, removing it leaves a gap that is filled by moving the conjugated verb (or the auxiliary) to the very first position, so the subordinate clause becomes structurally identical to an isolated yes/no question — but context, the comma, and the main clause that follows make clear it is a condition, not a question. This pattern works across tenses: in the present (Hat er Geld, kauft er es), in the hypothetical Konjunktiv II (Wäre ich du, würde ich bleiben), and in the unreal past conditional, which combines this word order with Konjunktiv II der Vergangenheit (Wäre er früher gekommen, hätte er sie getroffen).
Stylistically, the main clause sometimes opens with an optional so, whose function is to signal clearly that what preceded was a condition and not a stray question (Hilft er mir, so helfe ich ihm); this usage leans toward classical literature and highly formal texts, while modern journalism and official correspondence usually drop it and let the comma alone separate condition from consequence. One of the most widespread formulas in this pattern is Sollten Sie + Infinitiv, extremely common in corporate letters and official announcements: Sollten Sie Fragen haben, kontaktieren Sie uns — a polite, formal alternative to Wenn Sie Fragen haben sollten.
Compared with what you already know from earlier levels, where wenn was practically the only option for forming a condition, this construction is never used in everyday spoken conversation — using it in casual speech sounds stilted and out of place; its natural home is formal, literary, and legal writing. A common mistake among advanced learners is attempting to use this word order in spontaneous spoken language, or forgetting that the verb fronted to the beginning must be the conjugated verb (the auxiliary, if there is one) rather than the main verb, resulting in sentences that mistakenly front the Partizip II instead of the auxiliary hätte/wäre.