It's an understandable confusion. If you look at the refund page there's two bits of navigational text that say "Apply for a charter refund". The first, in the main section, takes you to further down the page where there's only mention of the paper form you have to print off, fill in and post. But! On the right hand side you'll see the same words: this is the magic link that takes you to the online form.
Applying for a refund is one of the most cathartic aspects of travelling by tube. We wrote a detailed guide a few years ago, but the main bits to remember are that if you're delayed for 15 minutes or more for reasons within TfL's control (like signal failure, for example), you should note the time, where you are and which line you're on, and then the time you reach your destination. And claim within 14 days.
TfL also today denied a rumour, outlined earlier this month on Commuting Expert, that it's considering increasing the delay time period from 15 to 30 minutes. Senior press officer Kristy Marshall told us:
As is good business practice we were reviewing our policies. The outcome of the review is that there will be no change to the length of delay before customers can claim for a refund of their single journey. It will remain at 15 minutes for the Tube.
Photo by unslugged from the Londonist Flickr pool