The Electoral Commission is satisfied that the National Party did not have to disclose two donations from merchant bankers Fay Richwhite before the 1996 election.
The donations are believed to be at the centre of a Serious Fraud Office investigation.
They were paid into a law firm's trust fund, controlled by former National party president Geoff Thompson in March. But the money was not transferred to the party until July when the new disclosure rules were in place.
Electoral Commission Chief Executive Paul Harris says the law requiring the disclosure of donations made to registered political parties came into force in April of that year and did not cover donations received before then.
The Commission will not be taking any further action.
However, a Serious Fraud Office investigation into the donation is continuing.
From April of 1996 even anonymous donations to political parties had to be registered. In that year National recorded none.
"Quite often donations were received through solicitors trust accounts or trusts to maintain anonymity. In this case that's how the donation was received," Thompson said on Monday night.
Meanwhile, National is still trying to find the whistle-blower.
The party meets in Auckland this weekend with a showdown likely between president Michelle Boag and her predecessor John Slater.
