Source of InvoiceSystem

TITLE:インボイス(適格請求書)制度 - The qualified invoice-based method (the invoice system)

- https://www.nta.go.jp/taxes/shiraberu/zeimokubetsu/shohi/keigenzeiritsu/invoice_about.htm

*. [#i298949e]

- https://www.freee.co.jp/solution/invoice/#content1