‘down the back of the sofa’: literal and figurative uses

The British- and Irish-English phrase down the back, or down the side, of the sofa, and its variants, refer to the loose change that has slipped down between the cushions and the back, or the arms, of a sofa.

This loose change can, nationwide, amount to staggering sums of money, as mentioned in The Guardian (London and Manchester, England) of Wednesday 8th February 1995:

DOWN THE DRAIN: Britons lost £40 million through holes in their pockets, down the backs of sofas and in other odd places last year. The Royal Mint said 450 million coins disappeared from circulation, including 25 million £1 coins.

Eric Wainwright had already mentioned this phenomenon in Only a penny, published in the Daily Mirror (London, England) of Friday 18th April 1952:

Has the penny had its day? Will it soon be rubbing shoulders with the farthing in the copper shadows of futility?
Since the bronze penny was first issued in 1860 2,760,000,000 have been minted—about a third of all the coins in circulation. Of these, 125,000,000 have been withdrawn, 175,000,000 sent to the colonies and 450,000,000 lost.
This means that nearly £2,000,000 worth of copper is lying disregarded in the backs of sofas, under the seaside pebbles and down the lining of worn-out suits.
But nobody cares.
The Royal Mint who can make about three pennies out of a pennyworth of bronze, don’t care.
And even the banks say that they have more pennies than they can cope with.

The variant down the side of the sofa occurs, for example, in an advertisement for AIB (Allied Irish Banks), published in several Irish newspapers in 1995—for example in the Sunday Independent (Dublin, County Dublin, Ireland) of Sunday 25th June:

An unexpected lump sum? It used to mean finding a half crown down the side of the sofa.
Nowadays, however, a windfall might prompt you to consider your savings and investment options.
To find out how you can make the most of a lump sum, talk to AIB.
LET OUR STRENGTH BE YOUR SECURITY.

The following letter and illustration are from Money writes, published in The Observer (London, England) of Sunday 9th July 1995—the British peer Lord Lucan (Richard John Bingham – born 1934) disappeared in 1974 after being suspected of murder:

I remember reading that there was confusion about whether I can old 5p and 10p coins to my bank to be exchanged for the replacement smaller coins. Could you please clarify this matter as I’ve just found a pile of them down the side of my sofa.

Dear Personal Finance,
I found Lord Lucan down the back of my sofa. I wonder if there is a reward for his return.

Katie Hannon used the phrase figuratively to denote public funds that are ‘miraculously’ found * in Demanding times for ‘rich Ruairi’, an article about the government in which the Irish Labour politician Ruairi Quinn (born 1946) was serving as Minister for Finance—article published in the Evening Herald (Dublin, County Dublin, Ireland) of Friday 21st February 1997:

In a futile effort to rein in their [= the Government’s] galloping public sector bill, Health Minister Michael Noonan drew a line in the sand with the nurses.
Four stabs at sorting it had seen their offer rise from £10m to £50m. That was the out and out limit, he said manfully. No way in the world could we afford another penny.
Then it sunk in. These were nurses. Regular Florence Nightingales. Suddenly somebody found another £30m down the back of the sofa.

* Cf.:
history of ‘money tree’ and ‘to shake the money tree’
‘no magic money (tree)’: justification for austerity

Jane Bussmann and David Quantick coined an extended variant of the phrase to designate permanent end in Forget about it, a list of the 1980s’ persons and things that are best forgotten, published in The Guardian (London and Manchester, England) of Saturday 30th May 1998—the one-pound note was withdrawn in 1988 in favour of the one-pound coin:

Pound notes Banknotes became things of value overnight as the small, friendly green-and-white pound went down the back of the Big Sofa In The Sky, along with the halfpenny. No longer would anything cost £9.99½.

Peter Howick used the phrase to illustrate the contrast between the ruling class and the people in the following from Memory loss must be very contagious, published in the Evening Herald (Dublin, County Dublin, Ireland) of Tuesday 7th March 2006:

Are our public representatives earning so much that cheques worth thousands are like loose change that fell down the side of the sofa?

The phrase refers to wasted money in the following from Martin Kelner’s column Screen break, published in The Guardian (London and Manchester, England) of Monday 30th November 1998:

This is an investment in the sense that you might invest your money in the drain in front of your house, or down the back of the sofa.

That disregarded small change can, however, turn out to be useful in times of crisis—as Judy Jones, Health Correspondent, wrote in Pay ‘cock-up’ leaves NHS staff penniless, published in The Observer (London, England) of Sunday 29th October 1995:

The cash crisis in the NHS hit a new and farcical low when thousands of employees left work on payday last week empty-handed.
Health staff, from the most senior managers and doctors down to the humblest clerks in Oxfordshire, Northamptonshire, Berkshire and Buckinghamshire, have spent the weekend raiding savings accounts, rummaging down the backs of sofas and begging tenners off neighbours to stave off temporary penury.

The British charity Comic Relief has used the phrase in the advertisements for the Red Nose Day telethon—in this one, for example, published in The Observer (London, England) of Sunday 9th March 1997:

SMALL CHANGE
BIG DIFFERENCE

We reckon there’s about 10 million pounds worth of small change in Britain that nobody misses. Down the back of sofas. In the pockets of old jeans. At the bottom of washing machines. And probably at the bottom of a lot of other things too. So why don’t you get foraging! Your small change could make a really big difference to some of the poorest people both here in the UK and in Africa. You’ll find a collection bag inside every Red Nose. To find out more about Red Nose Day, call 0891 55 77 88*. And remember, don’t forget to wash your hands.

COMIC RELIEF
RED NOSE DAY
MARCH 14TH ’97

* Calls cost 50p per minute Comic Relief Reg Charity No 326568