Markit said the Purchasing Managers Index for non-manufacturing businesses indicated a "robust expansion ... despite slower rise in new work," in the month.
The index, which shows expansion above 50, rose from December's 55.7 to 56.7, Markit said.
The index came in one tick higher than the flash estimate for the index released in late January.
The mark is also slightly higher than the four-year average for the service business purchasing managers index, which is 55.5.
The Institute of Supply Management, which releases a similar report, said their purchasing managers index also rose, climbing from 53 in December to 54 in January.
Their index for new orders rose from 54.3 to 56.3 and their employment index rose from 55.6 to 56.4.
Markit said the new business index slipped from 57.9 in December to 56.4. The employment index moved lower, sliding from 55.2 to 54.1. The business expectations index, however, moved higher, climbing from 78.7 to 80.8, Markit said.
"Despite disruptions caused by record low temperatures in parts of the country, business activity rose strongly again in both manufacturing and services," said Markit Chief Economist Chris Williamson in a statement.
"The pace of hiring ticked down slightly, but remains resilient as firms report the brightest business outlook for three years," Williamson said.
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