Kaji Anbun (家事按分): How Japanese Freelancers Split Home and Business Expenses
Almost every freelancer in Japan I’ve talked to works at least partly from home. Your apartment is also your office, your phone takes guest calls and calls from your mum, and the electricity bill pays for the laptop and the rice cooker. Japanese tax law has a name for splitting these mixed costs: 家事按分 (kaji anbun). It’s one of the most useful deductions a sole proprietor has, and one of the most often done badly.
I’ve done it for my own work and helped friends sort theirs out before 確定申告. The rule itself is simple. The hard part is the discipline around it, so here’s how I explain it over coffee.