Don't count out the possibility of a tax refund big enough to pay off a credit card or take a Caribbean vacation yet.

While early data from the Internal Revenue Service shows the average $1,901 refund to individuals in 2019 is about 8.8 percent lower than the same time last year, less than a fifth of U.S. tax returns have been filed so far.

And through May, when the bulk of individual returns are processed by the IRS, households will garner about $20 billion more than in 2018 through a combination of increased refunds and reduced payments, the Swiss lender UBS predicts.

That's welcome news for families already planning how to spend their money as well as for retailers who typically benefit from better-off consumers and GOP lawmakers who changed U.S. tax laws along party lines and found the results were more popular with businesses than individual voters.

Changes in this year's tax bills were driven by three causes, Robert Martin, a UBS economist, said in a report Tuesday. Fewer households will have to pay the alternative minimum tax, set up to ensure high earners with many deductions pay at least a base amount; a higher child credit will boost some refunds; and withholding tables used by employers were probably not adjusted correctly.

"The IRS tries to set withholding rates to minimize payments and refunds at filing," Martin explained. "Tax reform made meeting this goal hard."

A UBS team tracking the effects of increased refunds on retailers predicted married couples with two children earning less than $40,000 a year would be the biggest beneficiaries, with refunds jumping to an average $2,300 from about $500.

"This should be particularly beneficial to companies which are levered to the lower-income households," UBS noted. Among them are Dollar Tree and Dollar General as well as fast-fashion chains like H&M, the bank said.

Last year, the average tax refund during the first five months of the year was $2,778, slightly lower than in 2017. More than 102.5 million refunds were issued, with a combined value of $284.9 billion.

While U.S. law generally requires businesses to withhold enough money from workers' paychecks to cover their expected tax bill, employees can use so-called allowances to protect some of their salary.

In the past, Congress set the dollar value of each allowance, but the tax law changes of 2017 delegated that authority to the Treasury, which as of July had yet to establish written plans for consistently updating the withholding tables, according to the Government Accountability Office, the investigative arm of Congress.

"Many taxpayers have preferences about the tax refund that they will receive or the balance they will have to pay when they file their tax returns," the GAO wrote. Since "the tax-withholding tables that Treasury and IRS update each year are an important tool that both employers and employees rely upon to form their expectations," making sure they're accurate is crucial, the agency noted.