Move brings iPhone users in line with pricing model for BlackBerry, Android, and Windows Phone
Since its launch on Apple's iPhone, WhatsApp has charged users upfront to purchase the app. However, that upfront fee had meant that WhatsApp users on the iPhone also did not have to pay the subscription that the app's users on other platforms have had to.
The company currently charges a yearly subscription fee to users on Google's Android, RIM's BlackBerry and Microsoft's Windows Phone platforms.
The company hasn't set a date for when it will begin introducing the new subscription model. However CEO Jan Koum has said that it will "definitely [happen] this year", and that it was on the company's roadmap.
It also hasn't released details one when iPhone users will become liable to pay the fee – whether it will be all at once, or staggered based on their original purchase of the app.
Koum also put to bed rumours that the company was considering launching a non-mobile app. "We feel strongly that the the world is moving to mobile, and [so] we want to be mobile only."
WhatsApp currently handles more than 17 billion messages a day.