If you're thinking of selling an iPhone, especially now the new iPhone 5C and 5S have been launched, be warned that the price you get for it could soon plummet.

Data from mobile recycling website SellMyMobile.com suggests prices for older handsets could drop drastically after the expected announcement of the new model tonight, and further still once it hits shelves (see our Cheap iPhone guide for the best deals).

Its figures from this time last year, when the iPhone 5 was announced, show the trade-in price of the iPhone 4S – the iPhone 5's predecessor – fell sharply.

  • Two days before the iPhone 5 was announced (10 September 2012): The most you'd have got for recycling the iPhone 4S was £306.
  • The day of the announcement (12 September): The most you'd have got rose to £307.
  • Three days after the announcement (15 September): The maximum you'd have got decreased rapidly to £270.
  • The day the iPhone 5 was available to buy in-store (21 September): The maximum you'd have got for recycling the 4S fell to just £240.
  • A week after the iPhone 5 going on sale: The trade-in price of the 4S fell to £224 – a reduction of over 25% from the day of the announcement.

The newest iPhones were unveiled by Apple this evening. See our Apple launches new iPhones – and reveals prices news story for more.

When selling an old mobile, always compare the prices being offered using a mobile phone recycling price comparison service, such as MobileValuer, to ensure you're getting the best available.