Running a business
Consumption tax and the invoice system
The Invoice System Questions Thread is here. A rough translation of the NTA's FAQs is available here.
Depreciation of assets
The "useful life" figures that are used to calculate amortization/depreciation periods come from these regulations. The list is quite badly presented within the actual regulations, though. It's presented a little better at the NTA's site here, and the presentation at this site is more user friendly, but that's not an official source.
Tax optimization
Accounting
When running a business, some people choose to hire an accountant. If your business is very complex or you have no interest in the accounting side of the business, this is one viable option. However, it is quite expensive, both on a monthly basis and especially around tax filing season.
One alternative is to do your accounting, payroll and tax filing by yourself using cloud based accounting software such as Freee. This is a much cheaper alternative for both sole proprietors (個人事業主) and corporations (株式会社 or 合同会社). It’s also a good way to be more involved in the financial side of your business. However, it necessitates some knowledge of basic accounting.
Such services are aimed at the Japanese market, and therefore are all in Japanese. It can take a little while to get used to all of the accounting terminology, but once you get used it then many types of expenses and income fall under the same categories.