New York’s slow reopening has begun just in time for a virtual April 15 — Tax Day 2.0, pushed back three months by the novel-coronavirus pandemic. In a way, it’s the end of an era: The tax returns due to be filed on Wednesday will report incomes earned in 2019, the close of a decade-long economic expansion.

The wide-open, full-employment economy of the recent past is fast disappearing in the rearview mirror. Looking ahead, state and local governments in New York face an especially rough uphill climb back to even a semblance of normalcy.

Gov. Andrew Cuomo projected in April that the state income tax — by far Albany’s largest revenue source — won’t recover to fiscal 2020 levels for four years, opening the biggest budget gaps the state has ever seen. Even that outlook might prove overly optimistic, especially if (or when) the rejuvenated stock market wakes up to new economic realities. Mayor de Blasio’s latest financial plan assumes a faster, two-year recovery in city tax receipts — which seems almost delusional by comparison.

A large chunk of New York’s highest-earning 1 percent — who generate nearly half of the city’s ­income tax and more than 40 percent of the state income tax — fled the city when the pandemic hit. While most apparently retreated to second homes in neighboring counties of the tri-state area, thousands temporarily moved to more distant states — including low-tax Florida.

As if uncertainty surrounding the return of wealthy New Yorkers and the jobs they help support weren’t worrisome enough, there were clear signs of erosion at the high end of New York’s state tax base even before the pandemic.

Between 2010 and 2017, according to the Internal Revenue Service, the number of tax filers with incomes above $1 million rose 75 percent ­nationwide, but just 49 percent in New York. In 2017 alone, the number of millionaire earners rose 17 percent nationally, but just 10 percent in New York.

Migration data from the IRS point to a broader leakage. From 2011-12 through 2017-18, roughly 205,220 New Yorkers moved to Florida. While the annual number of Florida-bound New York filers didn’t vary much during this ­period, their average incomes nearly doubled to $120,023 in 2017-18, from $63,951 at the start of the period. Focusing on wealthy Manhattan, the incomes of Florida-bound New Yorkers rose at the same rate from a higher starting point— to $244,936 for 3,144 out-migrants in 2017-18, from $124,113 for 3,712 out-migrants in 2011-12.

These figures are from the ­period ending just before the new federal tax law temporarily virtually eliminated state and local tax deductions for high earners, raising New York’s effective tax rates higher than ever.

Oblivious to these trends and to the pandemic’s added centrifugal effect, 100 of the New York’s 213 state Assembly and Senate members recently signed a pledge to “raise taxes on high wealth” before reducing spending.

One proposal would fund schools with higher taxes on couples with incomes starting at $5 million — a bracket populated at last count by a mere 6,743 state residents, two-thirds of whom live (or used to live) in New York City.

Another would tax the “mark to market” gains of wealthy residents’ stock portfolios — although this would violate the state’s constitutional ban against taxing “undistributed profits” or “intangible personal property,” such as securities investments.

While Cuomo so far hasn’t embraced such ideas, he hasn’t flatly ruled out future hikes, either. But soak-the-rich tax sloganeering is hardly a welcome-home signal for high earners now on the fence about their futures in New York.

Meanwhile, pandemic-driven increases in federal spending have generated huge and growing budget deficits pointing to federal tax hikes — starting no later than next year if Democrats capture the White House and Congress. A restoration of SALT deductions, as pushed by Cuomo, will only drive federal rates that much higher on New York’s highest earners. The same goes for increased federal aid to the state and local governments, on which ­Cuomo is counting.

Either way, fiscal and budgetary trends in Washington will tend to further squeeze the top of New York’s income tax base. And even as the economy recovers, future tax days will be far less lucrative for the Empire State’s politicians.