The 28-year-old England captain agreed a four-year contract with the Spanish club on Tuesday, but just 7.5 million euros of the fee will be paid up front with another 17.5 million euros over the next four years in equal instalments, the English champions said in a statement.
Another 1.25 million euros will be due each time Real Madrid qualify for the Champions League over the next four seasons, and a further 1.25 million euros is payable if the nine-times European champions advance to the quarter-finals.
Proceeds from Beckham's sale will be used to support Manchester United's business development, including playing success at the highest level, Chief Executive Peter Kenyon said.
"While we are sad to see David go after so many great years at Old Trafford, we believe this is a good deal for the club," Kenyon said. Beckham joined the club as a schoolboy.
Married to former Spice Girl Victoria Adams, Beckham and "Posh Spice" have become Britain's number-one celebrity couple as his fame spread far beyond the world of football.
Last Saturday, the 28-year-old was awarded an OBE (Officer of the Order of the British Empire) by Queen Elizabeth.
