The BBC has reported that the Foyle MLA and three colleagues received donations of £2,700 from the Northern Ireland Friends of Israel but did not disclose them to the Electoral Commission.
Any extra costs for the trip were paid for by the Israeli Ministry of Foreign Affairs.
Mr Middleont and MLAs Michelle McIllveen, Jonathan Buckley, William Humphrey did report the donations to the Northern Ireland Assembly, but failed to disclose them to the commission.
Electoral Commission rules say that all MLAs must report any donation over £1,500 within 30 days.
The DUP told the BBC that the matter was an “administrative oversight” and that steps were being taken to rectify it.
A party spokesperson said that rules in the Assembly should be reviewed to align with those at Westminster.
MPs can report donations to the Parliamentary Commissioner for Standards and this information is then passed on to the Electoral Commission, but MLAs must report donations to both the NI Assembly and the commission themselves.
The DUP described the Israel visit as “aimed at developing economic links in such sectors as cyber security, with Israeli and Northern Ireland companies at the cutting edge of new technology in this specialist field”.
The trip was also attended by DUP deputy leader Nigel Dodds and MPs Ian Paisley, Jeffrey Donaldson, Emma Little-Penegelly, Gregory Campbell and Paul Girvan.
All of the MPs on the trip correctly recorded the donations with the commission.
The latest revelation comes after North Antrim MP Ian Paisley was handed a 30 day suspension from the House of Common after failing to disclose family holidays paid for by the Sri Lankan government.
He has also been suspended by the DUP pending an internal investigation.
The North Antrim MP was found guilty of paid advocacy after contacting then Prime Minister David Cameron to lobby on behalf of the Sri Lankan Government regarding a UN resolution.