That's about 12 per cent of all voluntary income. It's cost-effective, but it takes a long time to see returns. Not many donors are keen to discuss their own deaths, however, so how and when do you ask for a legacy from someone?
1. When to approach supporters
Ideally, charities should target supporters when they are rewriting their wills. People write their wills at key life stages, including the birth of a child, divorce, marriage and retirement. But the problem is that charities do not know when these happen.
"It's difficult to track when people are going to change their wills," says Richard Radcliffe, executive chairman of charitable legacy agency Smee & Ford. "You can't phone them up and ask them about it, so you have to engage them the whole time."
He suggests subtle contact on a regular basis; for example, indirect messages incorporated into newsletters increase the chance of coinciding with a supporter changing their will.
"Ideally, you would ask every week, but indirectly, so that you don't spoil the relationship," he says. "To send a donor a thank-you letter for a donation and then ask for a legacy would be deeply stupid."
Cancer Research UK focuses its legacy marketing on the 50-plus age group. Paul Farthing, its legacy fundraising director, advises targeting supporters who are approaching retirement age.
"These people may have another 30 years in which to leave legacies, but the propensity to change after that time reduces, so we want to get people reasonably early," he says.
CRUK tries to communicate with all kinds of supporters in that age group. "These aren't all wealthy people; we try to be inclusive," adds Farthing.
David Burrows, head of fundraising at agency TDA, suggests charities should reinforce messages to those in their 70s or older. "If you focus your campaigns on people aged below 50, you might be waiting 40 years to get a return on investment," he says.
2. How to ask
"People don't like jargon or overly flowery language," says Farthing. "Make sure the language is respectful and reasonably direct."
Radcliffe says: "The terms 'legacy' or 'bequest' are seen as deathly and as referring to huge sums of money. 'A gift in your will' is preferred. The balance is in asking them strongly enough to make them think, but subtly enough so you don't upset them."
He says that older people hate guilt-driven messages and horror stories. They prefer to give with joy rather than feel guilty that they are not saving another baby in Africa.
3. Which channels to use
"The majority of legacy income comes from supporters who are not already on the benefiting charities' databases," says Jonathan Parris, director of Remember A Charity. "To reach these new audiences, a mass-media approach is needed."
Parris adds that a consortium of charities can work together to deliver a more powerful campaign.
Burrows says print marketing is core, but retired people also surf the net a lot. Radcliffe says events are key: "Direct marketing isn't liked by some because it is seen as too personal. It's much better to try to meet people face-to-face so you can gain their trust."
CRUK runs events for 150 to 200 people, and smaller gatherings for a dozen people. "We include a speech from a scientist about our work and describe how people can leave a gift in their wills. It's a great way for supporters to hear about what we do," says Farthing. In the case of a small organisation, he says, volunteers and people involved in the organisation could communicate directly with supporters.
4. Presenting information
Older audiences may have poor vision, so all the experts agree that it is essential to use a large typeface, pictures, short lines of text and colour schemes that are easy to read. Online information should also be up to date and easy to access, with downloadable pages. It should also be easy to read.
5. Making it ordinary
"Be careful using celebrities," says Burrows. "For some people this confirms their objection that legacies are not for ordinary folk."
Radcliffe agrees: "People think legacies must be enormous, so make it clear that any size of gift is welcome."