There is a specific tax definition of passive income, known as “passive activity” to the Internal Revenue Service. Passive income is any income you make without actively working or are materially involved. The IRS defines it as any rental activity or any business in which the taxpayer does not “materially participate.” Nonpassive activities, or active activities, are businesses in which the taxpayer works on a regular, continuous, and substantial basis.

With passive income sources, you can go long periods of time without doing work, yet still earn income. In some cases, that income can expand without much additional input from you. For example, if I build a website in 5 hours and after a month, it has only made $50, my time to that point was worth $10/hour. It doesn’t stop there, however. In a year, if the site has earned $600, the value of those initial 5 hours grows to $120/hour. As time goes on, that number can continue to grow indefinitely.
Up to 2012, the taxpayer could opt for French savings income to be subject to taxation at source, with no further income tax payable in their annual tax return. This is known as a prélèvement forfaitaire libératoire (PFL). This option was abolished as of 1st January 2013, with the exception of taxpayers with income of less that 2,000 Euros per annum.
Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.