Connecticut’s coffers have continued to swell since the legislative session ended in early June — but now it’s too late for legislators to spend the money.

Gov. Ned Lamont’s administration recently reported tax revenues for the fiscal year that ended June 30 would be almost $400 million greater than it believed on June 4, when the General Assembly wrapped its regular 2025 session.

Coupled with revised estimates for federal grants, gaming receipts, fines, fees and other miscellaneous revenues, Lamont’s budget office now says Connecticut collected $420 million more in the fiscal year that ended June 30 than it had anticipated pre-June 4.

That’s more than double the $190 million post-session revenue surge the administration disclosed on June 20. And surging revenue just before the fiscal year closes on June 30 typically translates into extra revenue in the next year or two.

Legislators, who watered down several initiatives in the new budget they wrapped on June 4 — on the assumption finances weren’t as rosy — remain frustrated.

But an administration spokesman offered perspective Tuesday and said analysts made their best projections amid many unknowns.

“There remains significant international macroeconomic uncertainty over the past several years, including the pandemic, supply chain disruptions, tariffs, wars and uncertainty in the stock market as a result of President Trump’s ever-changing economic policies,” Lamont’s budget spokesman Chris Collibee said, adding that “missing by a modest percentage with all that analysis is unremarkable.”

An extra $420 million represents a little less than 2% of General Fund revenues.

But given that more than three-quarters of Connecticut’s budget is largely fixed by contract or other legal obligations, $420 million or 2% can be huge.

Legislative leaders said they needed at least $75 million extra this fiscal year to begin bolstering long-neglected Medicaid payments to doctors who treat the poor. They settled for $15 million.

An $84 million increase in grants for K-12 schools to mitigate a special education funding crisis became $30 million.

And a $600-per-child state income tax credit aimed at hundreds of thousands of households, which would cost government about $300 million per year, was deemed unaffordable.

Lawmakers instead approved a flat, $250 credit — regardless of the number of children in a household — but only to families making about $67,000 per year or less. It will cost the state $35 million annually.

The latest surge also is happening while Lamont is sparring with state employee unions over raises.

Four bargaining units have broken off talks with the administration since July 2, arguing they either were offered no raise or a lesser increase than Lamont and the legislature granted state police troopers in mid-May.

That agreement authorized a 2.5% cost-of-living hike plus a step adjustment for all but the most senior workers. A step adds roughly 2 percentage points to the value of the raise.

And these last-minute revenue surges, legislative leaders say, happen too frequently.

Since Lamont took office in 2019, his budget staff has upgraded revenue estimates by an average of $304 million in the first 2 ½ months after lawmakers leave the Capitol.

It’s also more than three times the $92 million average gap lawmakers dealt with between 2011 and 2018 under then-Gov. Dannel P. Malloy, according to state budget records.

“It’s occurring year after year,” Senate President Pro Tem Martin M. Looney, D-New Haven, told The Connecticut Mirror in late June. “It’s a pattern now.”

Administration officials note budget caps might have blocked more spending anyway, but lawmakers used several accounting maneuvers to work around those, often collaborating on them with the governor.

Democratic legislators aren’t the only ones concerned.

The House and Senate minority leaders Vincent J. Candelora of North Branford and Stephen Harding of Brookfield both have said unsuccessful GOP efforts to block tax hikes on corporations would have been aided by the knowledge that revenues already were on the rise.

Under the new budget, corporations will pay an extra $213 million in taxes over the next two years combined due to changes in income reporting and other rules. And a corporate tax surcharge that was supposed to expire would be extended to 2028, raising another $128 million over the coming biennium.

But even as corporate tax burdens rise, Connecticut closed the 2024-25 fiscal year with a projected $2.5 billion surplus, the second-largest cushion in state history and a windfall equal to almost 11% of the General Fund.

Chris DiPentima, president and CEO of the Connecticut Business and Industry Association, said that while he can appreciate “trying to be ultra-conservative” with revenue projections, asking corporations for an extra $340 million per year that appears unnecessary won’t help business confidence.

“Obviously we get concerned when there are business tax increases that are just going to a surplus as opposed to funding programs that are an absolute necessity,” DiPentima said.