You can't use two diffenent coupons for the same item
Only one coupon per item is permitted
If you want to tell a customer that a coupon/discount/etc. can't be used with another coupon, then you may simply state the terms of use for the coupons as exampled above.
I'm sorry but you can only use one coupon per purchase.
It's important to say "I'm sorry" at the beginning because the customer will be upset. "Per purchase" is a simple way to explain that they can only use one coupon at a time. I hope that this helps! :)
You can only use one coupon/discount voucher at a time
I'm sorry we only accept one discount voucher/coupon at a time
If you have a money off voucher then it can be called a 'money off voucher/coupon' or 'discount voucher/coupon'
If only one coupon can be used at one time then you could say 'you can only use one coupon at a time' or 'we only accept one coupon at a time' by adding I'm sorry it is a polite way of saying it
割引クーポンのことは、'money off voucher/coupon'または'discount voucher/coupon'と言えます。
クーポンの併用ができないのなら、以下のように言えます：
'you can only use one coupon at a time'（クーポンの併用はできません）
'we only accept one coupon at a time'（クーポンの併用はできません）
'I'm sorry'を加えると丁寧に言えます。
Sorry, per our policy, this coupon can't be used in conjunction with this discount.
Sorry, this coupon can't be combined with this discount.
per our policy' means 'according to our rules'. 'In conjunction with' means 'along with' -- e.g.: 'Helmets are used in conjunction with safety lights on bikes to prevent accidents.'
per our policy'は「当店の規定により」という意味です。
'in conjunction with'は「～と共に」という意味です。
例文：
'Helmets are used in conjunction with safety lights on bikes to prevent accidents.'
［訳］ヘルメットはセーフティライトと共に自転車の事故防止に使われます
I'm sorry but our policy is to only accept one discount coupon at a time.
You cannot use two coupons on the same transaction.
The best way to make the customer aware of the restaurant's policy is to politely state that "I'm sorry but our policy is to only accept one discount coupon at a time". This lets them know that this is out of your control and cannot be changed.
このレストランの方針について伝える最良の方法は、
"I'm sorry but our policy is to only accept one discount coupon at a time".（申し訳ございませんが、当店では一度に1枚の割引クーポンしか使えないことになっております）
と丁寧に説明することです。このように言うと、それが自分ではどうすることもできない、変えられないことだと伝わります。
You can't use this coupon if you are using another.
I am sorry but you can only use one coupon at oc time.
Unfortunately. you are not allowed o use m
Phases like "I am sorry, but..." as well as "Unfortunately..." are expressions that can used to when giving bad news like not being able to use a certain coupon.
"I am sorry, but..."や"Unfortunately..."などの表現は、例えばクーポンが使えないなど、悪い知らせを伝える時に使うことができます。
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