The singer was estimated to be worth between £10m and £15m following the huge success of her second album Back to Black.
However, she left just £4,257,580, reduced to £2,944,554 after debts and taxes were paid, when she died. The amount will be divided between her parents Mitch and Janis Winehouse.
The Daily Mail reports that Winehouse spent £1m on drugs between 2006 and 2008 and splashed out £500,000 on a holiday in St Lucia lasting a year and a half.
She also invested £500,000 in her protege Dionne Bromfield, gave Blake Fielder-Civil a £250,000 pay-off during their divorce, and spent £130,000 putting friend Alex Foden through rehab.
It is also claimed that Winehouse gave hundreds of thousands of pounds to friends for things including paying for their rent and for drugs.
"Before Amy died, money was being leeched off her left, right and centre. It was like taking money off a baby when it came to Amy - she couldn't stop giving it away. Mitch knew that most of it had probably been spent already," a friend said.
The 'Rehab' star was also a "soft touch" when it came to charitable campaigns. "If you asked her, she would do it. You just had to name it," a source commented.
Winehouse was director of Goal Music Productions Ltd, CW Touring Ltd, AW Promotions Ltd, Essney Ltd, Cherry Westfield Ltd and Lioness Records Ltd. Most had just a few thousand pounds in their accounts, while Cherry Westfield held a £2.3 million cash float.
Accountants had thought she may have more money tied up in investments and trusts.
Winehouse had a mortgage from Coutts Bank on her £1.8m, ten-bedroom house in Camden Square, spent £1,000 a month on her kittens, and would spend £20,000 in an afternoon at Selfridges on dresses, the report adds.
"Although she is very iconic, Amy actually didn't have a classic pop star's career in terms of earnings," the source went on. "She had one fairly successful album, Frank, and one very successful one, Back To Black, but she didn't tour at that point because of her personal problems.
"As everyone knows, these days the money is in the touring rather than simply the music. And then she never got it together enough to release any more music, so the money isn't that enormous."
Tim Southam, an accountant who has worked with various recording stars, described Winehouse's estate as a "conundrum".
Watch the video for Winehouse's 'Back to Black' below: