A domain would usually be considered an intangible asset & would NOT be considered a business expense & can be depreciated/expensed by its fair market value divided by determined useful life which ever is shorter and not to exceed 7 years. Your original entry would be cost of purchase if this was the situation. If you are to register domains and sell them for a profit, then your domains would be treated as inventory. Going this route, your domains are still an asset and can not be expensed. Your annual cost would be considered a cost of one unit & can be written on your books as your cost of goods purchases. If you renew a domain, you treat is just like a new reg. This situation, you will write in your books a loss no matter if you let it drop or renew it.