Royal officials said Tuesday the couple chose the date because they wanted a spring wedding. It also the feast day of St. Catherine of Siena, whose name Middleton shares.
Queen Elizabeth II married at the abbey, the 1,000-year-old church in central London where British kings and queens are crowned.
William and Kate decided against celebrating their nuptials at St. Paul's Cathedral, where William's parents married in 1981.
The palace said the royal family and the Middletons will cover the costs of the nuptials, apart from security.