我来结账;我来付账. I'll pick up the tab.=I'll pick up the bill.=It's on me.
晚饭/午饭我来请. The dinner/lunch is on me.
我要请你们喝酒. Have a drink on me.
我们何不各付各的? Why don't we go Dutch? (go Dutch各自付各自的)
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Try to translate this dialogue taken place in the restaurant!

Brown:Waitress,check,please.服务生,买单.
Waitress:Separate checks,sir?先生,分开算吗?
Brown:No,one check,please.I'll pick up the tab.不,一起算.我来结账.
Smith:You did last time,so this one is on me.上次是你付的,这次就我来付吧.
Brown:Did?Anyway,I'm buying today.是嘛?别管了,今天我买.
Smith:All right,if you insist.But the next one is on me.如果你坚持,就依你吧.但下次我买.
Brown:Ok.I will let you be a big spender next time.好,下次就让你好好请一顿.