A contractor who was on a list of banned state campaign contributors when he gave $10,000 to the Connecticut Democratic Party has rewritten the check to its federal account.

The Connecticut Democratic Party refunded John F. Fish, who owns Suffolk Construction Company, in December. But he turned around and legally rewrote the check to the Democratic Party’s federal account, which is supposed to support federal candidates and state party operations.

That’s according to the party’s latest January filing with the Federal Election Commission.

Suffolk Construction is a general construction contractor that provides pre-construction, construction management, general contracting, and design-build services nationwide, with offices in Boston as well as Irvine, Calif., Miami, and both Naples and West Palm Beach, Fla.

One of its projects in Connecticut was 360 State Street, a 31-story, 500-unit residential tower in New Haven. It’s also working on the Lawrence and Memorial Cancer Center in Waterford.

“The Connecticut Democratic Party relies on the information provided directly by donors on our contribution forms,” James Hallinan, a spokesman for the Connecticut Democratic Party, said in a statement Monday. “Additionally, we cross-reference donor information for non-federal contributions with information listed on the SEEC’s Prohibited State Contractors and Prospective State Contractors lists. If we identify any irregularities, we issue a refund to the contributor. If we identify any irregularities involving contribution limits, we issue a refund to the contributor. The Connecticut Democratic party acts in good faith and follows all laws, rules and regulations, and will continue to do so.”

The only other person to write a $10,000 check to the Democratic Party in January was Herbert Newman of Herbert Newman and Partners. Newman’s firm is redeveloping the New Haven coliseum and a building on Wesleyan University’s campus in Middletown. 

The Connecticut Democratic Party’s fundraising activities recently received an unsolicited advisory opinion from the State Elections Enforcement Commission, which without accusing the party of any wrongdoing tried to detail the nexus between state and federal party fundraising activity.

In general, “the federal account cannot spend its funds to make expenditures with the state account for Connecticut candidates for statewide office or the General Assembly,” the opinion from election regulators says. “The overarching principle to be followed is simple: Connecticut committees pay for their expenses with money raised within the Connecticut campaign finance system, i.e. from permissible contributions or public financing grants, properly reported under Connecticut law.”

However, there are some ways in which federal and state committees can share expenses on things such as staff and overhead. The federal fundraising report details how much time was spent by each employee of the party on federal campaign activity.

According to the filing, the party’s nonfederal share of its employees work was $110,524 and the federal share was $19,504.

The Connecticut Democratic Party raised $103,963 in January. Last year, it raised a total of $2.1 million to its federal account and about a quarter of that money came from $10,000 donors, some of whom do business with the state and its agencies.