a question about business expenses

Transportation, lodging and food. It may also include telephone calls, sometimes secretarial service, and 'technical' advise depending on the purpose of the business trip.

Here is a situation
if you work in a new company and have a business trip opportunity. after you negotiated with your client, you has been successful and secured an important new contract. You invite your client out to dinner at an expensive restaurant. However, at the end of the meal, he insists on paying the bill. it comes to $125.He passes your the receipt after he has paid and says you could claim this back on expenses. "everyone does it," he says.
What would you do in this situation?

Refuse it. Not only it is unethical, it will also raise you in yr clients esteem. If you accept it, then you are giving the impression of "if he can cheat on his company, he will definately cheat on me" to the client.

Agreed with Gautam. It is certainly not worth the risk.

Not a matter of "not worth the risk." It's plain and simple unethical behavior.