How to ensure that your child does not run up unexpected bills while playing games on your Apple or Android device.

A five-year-old boy has run up a £1,700 ($2,550) bill in just ten minutes while playing on his parents' iPad.

Danny Kitchen asked for the passcode for the device so that he could download a game, Zombie v Ninja, from the Apple store. But after downloading the free app Danny found his way into the game's online store and innocently ordered dozens of costly add-ons - totaling £1,710.43.

His mother knew nothing about the spending until she saw a series of emails from iTunes the following day listing what he had bought.

The term "freemium" was coined to describe the practice of offering a free app that then has expensive enhancements.

These “in-app purchases” might include virtual credits for buying items in the game, special abilities for game characters, additional levels not accessible in the free version of the game, or the ability to skip a level that might be challenging. Some games charge as much as £70 per purchase.

Fortunately, it's possible to turn off in-app purchases. Here's how to do it.

Google Android

Open the Google Play Store app and choose 'Menu' and then 'Settings'. Under 'User Controls' you'll find an option to 'Set or Change PIN'. Tap this and Android will ask you for a PIN. Type your chosen PIN, tap OK and then re-enter the PIN to confirm. Then tick the box next to 'Use PIN for purchases'.

Once you've done that, anyone who wants to make an in-app purchase on your device will need to know the PIN. That should keep your bills secure from little fingers.

Apple iOS

The Restrictions menu in Apple iOS lets you control all kinds of things. You can send a password for in-app purchases or turn them off altogether. It's possible to prevent apps being deleted or installed and control access to age-restricted content.

To prevent in-app purchases in iOS, open 'Settings' then choose 'General' and 'Restrictions'. Then tap 'Enable Restrictions', choose a PIN and enter it a second time to confirm. Now you can set any restrictions from the menu below. In the 'Allowed Content' menu, slide 'In app purchases' to 'Off'.

Amazon Kindle Fire

The Kindle Fire is an Android-powered tablet but the operating system has been modified by Amazon so the process for restricting in-app purchases is a little different. Start by opening the Amazon Appstore app. Choose 'Menu' and then 'Settings'. Then tap 'Parental Controls', choose 'Enable Parental Controls' and enter your Amazon password. If you'd prefer to choose a PIN, then tick the 'Use PIN' box.