DES MOINES — State tax collections took a 9.1 percent plunge last month, but the decline was not due to the COVID-19 pandemic but rather to the state more quickly getting tax refunds to individuals and corporations, according to the Legislative Services Agency.Overall, state tax receipts stood at $5.825 billion at the end of March — a 4.2 percent increase of $233.6 million over the first nine months of fiscal 2019 — despite a $34.3 million decline in the monthly collections, said Jeff Robinson, a senior tax analyst at the Legislative Services Agency.The state saw monthly growth in its three major revenue categories of personal income tax, sales/use and corporate income tax.But March’s numbers were pulled down by a spike in tax refunds paid out — $70 million more than in March 2019 and about $100 million more over the past two months, Robinson noted.But the March report may be the last vestiges or normalcy, with businesses slated to remit sales tax receipts and income tax withholdings by mid-April.That’s when Robinson said he expects the state revenue numbers to start to get “weird” as the negative economic effects of the COVID-19 pandemic start to surface.“We’re going into a black hole of not knowing what’s going on.” he said.This month is when the effects of Gov.