お客様に

to the customer or guest

→ 御客様
phrase Rare #37,002
to the customer or guest お客様 is a polite term for a customer or guest, and に marks the person who receives something or is affected by an action.
JA: お客様に料理をお出しします。
EN: We will serve the customer the meal.

その子はお客様に無作法にしたことで謝るべきだ

That child should apologize for being rude to the customer.

お客様にお茶を出して

Please serve the customer some tea.

お客様に出す直前です

It’s just about to be served to the customer.

— レミーのおいしいレストラン (2007)

いつお客様にこの招待状お送りしましょうか

When should we send this invitation to the customer?