至于: as for, as to
【六16】介词 / prepositions
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
至于 moves the conversation to a second topic that is related to the first but not settled by it: “as for…”, “when it comes to…”. It sits at the head of its clause, followed by a noun or noun phrase, then a comma and the comment: 时间已经定了，至于费用，还需要再讨论.
The first topic must already be on the table: 至于 never opens a text. It is used to go through the items of a file (price, then payment, then deadlines) and stays polite and slightly formal. In a negotiation it is the word that says “that point is closed, let's move on to the next”.
Do not confuse it with 关于 (hsk3-g47, the overall subject: “about”) or 对于 (hsk4-g14, an attitude towards something). 不至于 (hsk5-g18, “it won't go that far”) is a different word.
Examples
价格我们可以谈，至于支付方式，就按合同来。
Jiàgé wǒmen kěyǐ tán, zhìyú zhīfù fāngshì, jiù àn hétóng lái.We can talk about the price; as for the payment method, we follow the contract.
明天的会九点开始，至于地点，我下午再通知大家。
Míngtiān de huì jiǔ diǎn kāishǐ, zhìyú dìdiǎn, wǒ xiàwǔ zài tōngzhī dàjiā.Tomorrow's meeting starts at nine; as for the venue, I'll let everyone know this afternoon.
机票已经订好了，至于住的地方，我们到了再找吧。
Jīpiào yǐjīng dìng hǎo le, zhìyú zhù de dìfang, wǒmen dào le zài zhǎo ba.The plane tickets are booked; as for where to stay, we'll look when we get there.
我只负责技术问题，至于销售，你得问王经理。
Wǒ zhǐ fùzé jìshù wèntí, zhìyú xiāoshòu, nǐ děi wèn Wáng jīnglǐ.I only handle technical issues; as for sales, you'll have to ask Manager Wang.
他的建议很有道理，至于能不能实现，还要看条件。
Tā de jiànyì hěn yǒu dàolǐ, zhìyú néng bu néng shíxiàn, hái yào kàn tiáojiàn.His suggestion makes good sense; whether it can be carried out depends on the conditions.
Common mistakes
✗ 至于这本小说，我昨天买了。 → ✓ 这本小说我昨天买了。(at the start of a text, 至于 has no earlier topic to move on from).
✗ 价格很高，至于质量很好 → ✓ 价格很高，但质量很好 (至于 changes the topic, it does not express contrast).