When Are Entertainment Expenses Deductible?

General Rule You can deduct ordinary and necessary expenses to entertain a client, customer, or employee if the expenses meet the directly related test or the associated test.
Definitions
Entertainment - includes any activity generally considered to provide entertainment, amusement, or recreation, and includes meals provided to a customer or client.
An ordinary expense is one that is common and accepted in your field of business, trade or profession.
A necessary expense is one that is helpful and appropriate, although not necessarily indispensable for your business.
Tests to be Met Directly-related Test:
Entertainment took place in a clear business setting, or
Main purpose of entertainment was the active conduct of business, and you did engage in business with the person during entertainment period, and you had more than a general expectation of getting income or some other specific business benefit.
Associated Test
Entertainment is associated with your trade or business, and 
Entertainment directly proceeds or follows a substantial business discussion.
Other Rules
You cannot deduct the cost of your meal as an entertainment expense if you are claiming the meal as a travel expense
You cannot deduct expenses that are lavish or extravagant under the circumstances.
You generally can deduct only 50% of your un-reimbursed entertainment expenses.