FILE PHOTO: A security camera hangs near a corner of the U.S. Internal Revenue Service (IRS) building in Washington May 27, 2015. REUTERS/Jonathan Ernst/File Photo

WASHINGTON (Reuters) - The first U.S. tax filing season under the overhaul that President Donald Trump signed into law at the end of 2017 got off to a slow start in the first week, with data released on Friday showing a significant drop in returns and refunds.

According to the Internal Revenue Service, the total number of returns received in the week ending Feb. 1, 16.04 million, was down 12.4 percent from the week that ended on Feb. 2, 2018. Only 13.31 million returns were processed, down 25.8 percent from the year before. The average refund of $1,865 was 8.4 percent smaller than the average refund in the period last year.

The partial government shutdown - at 35 days, the longest in U.S. history - ended three days before the tax filing season officially opened on Jan. 28. The final deadline is Apr. 15.

Republicans passed a $1.5 trillion tax overhaul in the final weeks of 2017 that cut rates for both individuals and corporations, giving fellow Republican Trump a major policy victory. Democrats had warned that the cuts and other changes in the overhaul would primarily benefit the country’s wealthiest, and many are eager to see how it will affect average Americans.

Treasury Secretary Steven Mnuchin said in a statement on Friday that the 2019 “filing season has successfully launched with millions of tax returns having been filed.”