(CNN) Tax season is off to a slower start this year, with early filers seeing smaller average refunds.

The average refund is down about 8% under the first full year of the overhauled tax code, according to data released by the IRS on Friday. Refunds averaged $1,865 compared to $2,035 for tax year 2017.

The total number of returns received also dipped during the first week of the season ending February 1, down from about 18 million to some 16 million so far in 2019.

This season will be watched closely to gauge the real impact of the Republican-led tax overhaul in 2017 that ushered in the most sweeping changes to the tax code in 30 years.

The new rules lowered most individual rates and nearly doubled the standard deduction. The legislation also included sweeping tax cuts for companies, lowering the corporate rate to 21% from 35%.

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