On the tenth day of Christmas I'm feeling like Santa  Clause, let's sponsor something for a good cause.
You can deduct 100% of the cost of entertainment you supply to the general public for charitable purposes.

On the ninth day of Christmas I've escaped in the car. I need a meal since I've travelled oh so far.
If you or one of your employees buys a meal while travelling on business, the cost is 100% deductible. That's despite the rule that says food and drink provided away from your business premises is only 50% deductible. However, you can only deduct 50% if the travel is mainly for the purpose of entertainment, if the meal or function involves and existing or potential business contact, or at a celebration meal, party, reception or similar while you are travelling. You can deduct 100% of the food and drink you provide at a conference, education course or similar event that lasts for four hours or more.

On the eighth day of Christmas my secretary wants from me, some chocolate biscuits for her morning tea.

Light refreshments, like morning and afternoon teas, are 100% deductible.

On the seventh day of Christmas my staff want from me, a bonus (preferably tax free).

A cash bonus is taxable income to your employee and will be subject to PAYE. Income to the employee, fully deductible expense for the employer.

A gift voucher that is in lieu of cash is treated as a cash bonus. 

You can generally claim 100% of the cost of gifts, such as food baskets or event tickets.

On the sixth day of Christmas we've got to book the hall, everyone is invited – one and all!

As the event is open to the public, it is 100% deductible expenditure. You would be able to claim all the food, drink and other associated costs.

On the fifth day of Christmas they're now telling me, "Inviiiiiiiiite all the cliennnnnnnnnts!"

But as only clients are invited, the event is only 50% deductible. In order to claim 100%, the function must be open to the public.

 On the fourth day of Christmas my staff want from me, a Christmas party at the Pear Tree.
Food and drink provided away from your business premises is only 50% deductible.

On the third day of Christmas to appreciate their hard work, I'll give my staff a Christmas party at work.
You can only deduct 50% of the cost of food and drink you provide at your business premises (other than light refreshments). This includes a social event, eg, celebration meal, party, reception or in an area restricted to senior employees, such as an executive dining room. This rule applies whether the entertainment is provided to staff or to guests invited from outside the business. If you provide entertainment that's  only 50% deductible, you can only deduct 50% of any supporting costs such as hire of crockery, glasses, waiting staff and music.

On the second day of Christmas my business gave to me, less tax to the IRD. 
Read what you need to know about tax considerations of the holiday season including the staff party and Xmas bonus in our latest blog "The Grinch that Taxed Christmas".