The Electoral Commission is looking into a DUP dinner hosted by North Antrim MP Ian Paisley.
The commission is understood to be focusing on £1500 paid by Mid and East Antrim Council to sponsor a table at the dinner.
The event was attended by Conservative Minister Michael Gove.
The council insists the money was paid to Tullyglass Hotel, Ballymena, which hosted the dinner and not to the DUP.
A letter leaked to the BBC revealed Ian Paisley asked the council to make a cheque payable to the hotel but to send it to the DUP offices in Ballymena.
Under Electoral Commission rules, councils are not considered “permissible donors” and donations received from such bodies must be returned within 30 days.
It is understood the commission is assessing the information which has recently come to light before deciding whether or not to launch a full investigation.
In a statement the commission said: “We are aware of this matter and are considering it in line with our enforcement policy.”
The DUP declined to comment on the commission’s intervention but has, in the past, insisted the dinner in November was not a party fundraiser.