INCOME TAXES	9 Months Ended
Sep. 30, 2013
INCOME TAXES [Abstract]
INCOME TAXES	(E) INCOME TAXES The significant combined statutory federal and state income tax rate for UIL Holdings for the three- and nine-month periods ended September 30, 2013 and 2012 was 40.9%. Differences in the treatment of certain transactions for book and tax purposes occur which cause the rate of UIL Holdings’ reported income tax expense to differ from the statutory tax rate described above. The effective book income tax rates for each of the three- and nine-month periods ended September 30, 2013 were 44.8% and 37.5%, respectively, as compared to 40.7% and 40.5% for each of the three- and nine-month periods ended September 30, 2012. The increase in the effective book income tax rate for the third quarter of 2013 compared to the third quarter of 2012 is due primarily to the impact of provision to return adjustments recorded in the third quarter of 2013 as compared to the third quarter of 2012. The decrease in the effective book income tax rate for the 2013 year-to-date period is due primarily to lower CTA amortizations and higher equity allowance for funds used during construction.

INCOME TAXES

9 Months Ended

Sep. 30, 2013

(E) INCOME TAXES

The significant combined statutory federal and state income tax rate for UIL Holdings for the three- and nine-month periods ended September 30, 2013 and 2012 was 40.9%.

Differences in the treatment of certain transactions for book and tax purposes occur which cause the rate of UIL Holdings’ reported income tax expense to differ from the statutory tax rate described above. The effective book income tax rates for each of the three- and nine-month periods ended September 30, 2013 were 44.8% and 37.5%, respectively, as compared to 40.7% and 40.5% for each of the three- and nine-month periods ended September 30, 2012. The increase in the effective book income tax rate for the third quarter of 2013 compared to the third quarter of 2012 is due primarily to the impact of provision to return adjustments recorded in the third quarter of 2013 as compared to the third quarter of 2012. The decrease in the effective book income tax rate for the 2013 year-to-date period is due primarily to lower CTA amortizations and higher equity allowance for funds used during construction.