最常用的用法，其他类似表达：pick up the bill; foot the bill
Can we have the bill please?
麻烦，买单。
take the check
check 在这里指“账单”的意思，也可以作动词表"买单"
We'll take the check./ Check, please.
我们买单。
It's on me
我请客算我账上; 美国常用俚语：我请客;店老板请客：It's on the house(店里免费赠送)
On me this time.
这次我请客。
Be my guest
“请便， 不用客气”类似于help yourself to it.
Be my guest. Please order whatever you want to have.
晚餐我请，你想吃什么随便点吧。
My treat/It's my treat
"treat“ 除了有"对待"的意思,它还可以表示"款待、招待";比如 你和别人打赌输了之后，You had to treat her to an ice cream. (你不得不请她吃冰淇淋)
"treat"还有"名词"的身份，表示"请客、做东"; Let me get this 也可表示 "做东"，常用于口语
I'm buying/paying.
进行时表将来：等一下我来买单
Listen, please don't argue with me. I'm paying tonight.
行了，都别跟我争啦。今晚我来买单吧。
This is my round.
这次轮到我付钱; round 有“回合” 的意思
其他有关付账的表达：
Please add to my account.
请记在我的账里。
Let's split the bill.
我们分开付账吧。
Shall we split the check ?
我们大家平摊?
We'd like to pay separately.
我们分开埋单。
Separate check, please.
分别买单，谢谢。
Let's go Dutch this time.
这次咱们AA制吧。
Let's go halvsies.
我们各付一半吧。
How about we pay our own share?
我们各付各的如何?