Nov. 20 (Bloomberg) -- Royal Bank of Scotland Plc, sold $7 billion of debt due in March 2012, according to data compiled by Bloomberg, equaling the largest U.S. corporate sale since May.

The government-backed issue was split between $2 billion of fixed-rate notes that priced to yield 80.5 basis points more than similar-maturity U.S. Treasuries and $5 billion of floating-rate debt that pay a spread of 26 basis points more than the three-month London interbank offered rate, Bloomberg data show. A basis point is 0.01 percentage point.

Proceeds from the sale of the notes, which may receive top ratings from Moody’s Investors Service and Standard & Poor’s, will be used for general corporate purposes, according to a person familiar with transaction, who declined to be identified because of lack of authorization to speak on the record.

The sale was the biggest in the U.S. corporate market since RBS sold $7 billion of three-year government-backed debt in May, according to Bloomberg data. That offering also was split between fixed- and floating-rate notes. The $4.5 billion of fixed-rate notes paid 124.5 basis points more than U.S. benchmarks, and the $2.5 billion floaters paid 70 basis points more than Libor.

Chancellor of the Exchequer Alistair Darling established a guarantee program in response to the credit crunch that allows financial companies to sell bonds with government guarantees.

The U.K. Treasury agreed earlier this month to inject 25.5 billion pounds ($42.1 billion) of capital into Edinburgh-based Royal Bank of Scotland, increasing its stake to 84.4 percent from 70.3 percent.

Neil Moorhouse, a spokesman for Royal Bank of Scotland, Britain’s biggest government-controlled bank, didn’t return calls and e-mails requesting comment.

To contact the reporters on this story: Gabrielle Coppola in New York at gcoppola@bloomberg.net; Nikolaj Gammeltoft in New York at ngammeltoft@bloomberg.net

Last Updated: November 20, 2009 17:13 EST