"How many tickets" does not look like a complete sentence. Is it okay to skip the rest of the sentence?
Native speaker’s answer
Rebecca
The rest of the sentence is implied here, the full implied sentence is "How many tickets do you need, please." It is okay to omit the rest of the sentence because the listener understands what the full intended sentence is. If you want to make sure you are clearly communicating, or are speaking to someone who might not understand a shortened sentence, you can use a full sentence.