This hard-fought-for policy united local political parties, but doubt now hangs over it.
There are several reasons why. Firstly, although the legislation is in place, it needs a final green light from government.
The Northern Ireland Executive must demonstrate its finances are on a sustainable footing.
Does a potential £490m blunder over the Renewable Heat Incentive (RHI) scheme undermine that?
This is, perhaps, arguable.
We are talking about finding £20-30m a year for 20 years to cover an RHI overspend, a small part of a £10bn annual block grant.
But the crisis has put other hurdles on the horizon.
The Northern Ireland Assembly must pass a rate recommended by the finance minister in the year before it applies.
How soon will there be an executive or assembly the other side of an election?
And will there then be a greater reluctance about paying for corporation tax with a £200m cut to the block grant?
Any return to direct rule from Westminster might not offer an immediate solution either.
European Union state aid rules apply until Brexit and they only allow devolution of corporation tax to a region which has "institutional autonomy".
It is premature to pronounce Northern Ireland's big economic idea as dead.
But in the here and now, things look mightily challenging - can Invest NI promote a rate and a date to overseas companies with any certainty?
Even before the political crisis, some experts felt 2018 was ambitious anyhow for companies to adapt to new rules.
And all the while, the main UK rate of corporation tax is falling, blunting the attractiveness of what Northern Ireland wants to offer.

Mr Yanukovych flew from China to Sochi in southern Russia for the meeting. He also cancelled a visit to Malta.
Last month he shelved a partnership deal with the EU, triggering angry protests in Ukraine's capital Kiev.
Jailed opposition politician Yulia Tymoshenko has reportedly called off a prison hunger strike.
The former prime minister's daughter, Eugenia, said her mother had accepted a request from protesters in Kiev to stop the fast.
She had reportedly begun the hunger strike on 25 November in protest at Mr Yanukovych's failure to sign the EU deal.
Thousands of anti-Yanukovych protesters remain outside the government building on Kiev's Independence Square, braving bitter cold.
They are furious that he made an 11th-hour U-turn in relations with the EU, refusing to sign the association agreement that had been prepared during years of negotiations.
In Sochi, Mr Yanukovych discussed "preparation of a future treaty on strategic partnership" with Russia, his press service said.
The talks covered various economic issues, the statement said, without elaborating.
Mr Putin has been urging Ukraine to join Russia's customs union with Belarus and Kazakhstan - a union whose entry terms are far less demanding than the EU's.
In recent months Russia has put Ukraine under economic pressure, imposing long customs delays at the border and banning imports of Ukrainian sweets.
Arseniy Yatsenyuk, a Tymoshenko ally and leader of the main opposition faction in parliament, condemned the talks in Sochi.
"Their attempts to sell Ukraine to Russia have not ended in any way," he said.  "If Yanukovych tries to sign anything with Russia about the customs union it will lead to a bigger wave of protests."

28 December 2015 Last updated at 20:11 GMT
The woman's husband was rescued from the blaze and is being treated in hospital.
Clodagh Rice has been to the scene.
Northern Ireland's political crisis could kill off plans to cut corporation tax to 12.5% in April 2018.
[NEXT_CONCEPT]
Ukraine's President Viktor Yanukovych and his Russian counterpart Vladimir Putin have held surprise talks on a "strategic partnership treaty".
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An elderly woman has died in a house fire in Enniskillen.