The real trade-offs between staying a sole proprietor and forming a company, and the signals that tip the balance.
Incorporating can cut tax at higher profits and add credibility and liability protection, but adds fixed costs, paperwork, and social-insurance obligations — most people incorporate once stable profit, client requirements, or growth plans justify the overhead.
A sole proprietorship is the lightweight default: near-zero setup, simple filing, and full control. A company (法人) is a separate legal person, which brings three things people incorporate for — potential tax efficiency at higher profit, because corporate rates top out well below the highest personal income-tax rates; limited liability, separating business risk from personal assets; and credibility, since some clients prefer or require billing a company. Against that sit real costs: incorporation fees, annual local taxes even in a loss year, mandatory enrollment in employees’ social insurance, more complex accounting, and, for almost everyone, a tax accountant.
There is no single magic number, but the tipping point is usually a combination: profit that is high and stable enough that the tax gap outweighs the fixed overhead, plus a non-tax reason such as hiring, raising money, signing bigger contracts, or clients that will only deal with companies.
Watch for concrete signals rather than a round revenue figure. Your profit has been comfortably into the higher personal-tax brackets for a while; consumption tax is now unavoidable and a company’s two-year exemption window could help timing; you want to pay yourself a salary and split income across a household; you are hiring staff; or a major client insists on contracting with a company. Any one of these can justify the move; several together make it clear.
If the signals are there, model it properly before filing paperwork. A tax accountant can compare your specific tax and social-insurance outcome as a proprietor versus a company, and incorporation services from freee and Money Forward can prepare the documents once you have decided. The companion guide on company types then helps you choose between a GK and a KK.
Company incorporation · freee K.K.
A guided online service that prepares the documents to incorporate a KK or GK, walking first-time founders through the registration steps.
Fees: Service tiers plus separate statutory registration costs — verify current pricing.
Company incorporation · Money Forward
Money Forward’s online incorporation service that generates the paperwork for a KK or GK and connects into its cloud accounting suite.
Fees: Service plus separate statutory costs — verify current pricing.
Find a tax accountant · Bengo4.com
A directory and matching service that helps individuals and businesses find a tax accountant (税理士) by specialty, area, and fee.
Fees: Matching is free to users; the accountant’s own fees apply — verify with each firm.
There is no single magic number; incorporate when stable, higher profit makes the corporate-tax advantage outweigh the added fixed costs, and usually when a non-tax reason also applies — hiring, raising money, bigger contracts, consumption-tax timing, or clients that will only bill a company. A company adds incorporation fees, annual local taxes even in a loss year, mandatory employees’ social insurance, more complex accounting, and typically a tax accountant. Model your own tax and social-insurance outcome as a proprietor versus a company with a 税理士 before deciding.
A godo-kaisha (GK) is cheaper and simpler to form and run — no articles-notarization fee and a lower registration tax — with the same limited liability, so many solo founders start there. A kabushiki-kaisha (KK) costs more but has the strongest public recognition and can issue shares to raise capital, which matters if you expect investment or enterprise clients that prefer a KK. You can convert a GK to a KK later. Fees, capital, and governance rules are statutory and change, so confirm current requirements before filing.