Just guessing here--strictly a guess--so take it for what it is worth:
Individuals who own an interest in a pass-through entity like a partnership or S Corporation might be receiving a pass-through credit for their individual returns if the entity is on a fiscal year other than a calendar year. Most pass-through entities are on calendar years, but there are a few that do operate on a fiscal year.
If ABC Partnership is on a July 1, 2016, to June 30, 2017, fiscal year, and ABC installed EVSE before 12/31/16, then the credit will flow through to the partners on schedule K-1 on the 2016 partnership tax return (forms for tax years always are used for the year in which the fiscal year begins.) However, the partners will report the income, loss, deduction, or credit on their 2017 returns, since 2017 is when the tax period for ABC ended.
About 30 years ago legislation was enacted to do away with fiscal year flow-through entities unless some very strict exceptions were met or a Section 444 election was in place. Congress got tired of individuals deferring income taxes up to 10 months by those taxpayers who held substantial interests in partnerships, S Corporations and fiduciaries.
Unless you are affected by such an entity, and you know that this entity will be passing through the EVSE credit, just complete your return at your leisure!