The fine is a sanction against the DUP man for accepting money from two councils for attendance at a fundraising dinner.
The event was addressed by the senior Conservative Michael Gove.
Mid and East Antrim and Causeway Coast and Glens councils took tables at the dinner at Tullyglass hotel in Ballymena in September 2017, each paying £1,500, the BBC reports.
The councils said the payments had been made to the hotel for attendance at a business related event, the BBC report continued.
A DUP spokesperson said the event was not organised by the party but by Mr Paisley in his capacity as MP for North Antrim and the associated donations were received on that basis.
“Mr Paisley cooperated fully with the investigation and, while acting in good faith, he accepts the outcome of the report,” the spokesperson added.
The commission decided the dinner was a fundraiser and councils are not regarded as legally “permissible donors” for political parties.
It is understood the North Antrim MP has agreed to return the money to the councils and the £1,300 fine is in addition to that, the BBC said.
The fundraising dinner was not the first time Mr Paisley has been in trouble over financial matters.
In July 2018, MPs voted to suspend him for 30 sitting days.
It followed his failure to declare two family holidays paid for by the Sri Lankan government in 2013.
In 2014 Mr Paisley wrote to the prime minister to lobby against supporting a UN resolution on Sri Lanka over alleged human rights abuses.
By failing to declare his trips, Mr Paisley “breached the rule against paid advocacy”, a Westminster standards committee said.
In 2008, Mr Paisley resigned as a junior minister at the assembly following criticism over his links to developer Seymour Sweeney and allegations he lobbied on his behalf.
An ombudsman ruled there was no evidence to suggest he had broken assembly rules, but he stepped down, saying: “The criticism has been a distraction and has got in the way of the activities of this government and importantly it has gotten in the way of the activities of my political party.”
The Electoral Commission is the official watchdog, which regulates the funding of political parties in the UK.
It says the fine has been imposed due to Mr Paisley’s “failure to return donations from impermissible donors within 30 days of receiving them”.
A commission statement says the two variable monetary penalties totalling £1,300 have to be paid by 8 October 2020.
In a statement to ‘Ballymena Daily’, a Mid & East Antrim Borough Council spokesperson said: “Council received an invitation to a North Antrim Annual Business and Community dinner hosted and facilitated by Ian Paisley MP, with special guest Rt Hon Michael Gove MP, then Secretary of State for Environment and Rural Affairs, and sponsored by Belfast International Airport.
“Elected Members at full council in August 2017 agreed, without objection, to purchase this table and the event was attended by Elected Members from different political parties, senior officers and representatives from the agri-food sector across the borough to avail of the opportunity to discuss first-hand with the Minister their issues and concerns in relation to the agri-food sector post-Brexit.
“Council was requested to make payment to The Tullyglass Hotel and did so electronically.
“Mid and East Antrim Borough Council takes its responsibilities in relation to financial prudence and accountability very seriously.”
Philip McGuigan, Sinn Féin assembly member for North Antrim, said it was “frankly unacceptable that a local council used ratepayers’ money for what was essentially a party political fundraiser”.
“I called on the Electoral Commission to conduct an investigation into the matter at the time and welcome that has now been concluded,” he said.
“Local councils should represent everyone. It is equally unacceptable that the DUP consciously or otherwise failed to declare this donation.”
In a statement, North Antrim TUV leader Jim Allister said: “It is of course nothing new for Ian Paisley to find himself in the middle of a scandal. Over the years in which he has held office either as a junior minister or MP it seems that the scandals come one after another and that when one report is completed we are just waiting for the next one to appear.
“So it is today with the findings against him by the Electoral Commission into the Tullyglass dinner. Whether there will be a further report from the Parliamentary Standards Commissioner to on overseas trips remains to be seen.
“Having read the information released by the Electoral Commission a number of pertinent questions remain unanswered. For example, did Mr Paisley directly receive the monies paid by Mid and East Antrim and Causeway Coast and Glens councils? (If so, why would councils agree to such an arrangement?), or is he being deemed to have received it as a beneficiary?
“How much of the money was actually paid to the hotel? Did the Commission have to instruct Mr Paisley to pay the monies back to the councils, was there a time limit on him doing so and if there was did he meet it? Indeed, it is even unclear if the monies have yet been paid back.
“These are all questions which Mr Paisley needs to address. The fact that they have to be asked at all is testament to the damage being done to Unionism and the standards expected of an MP.”