The Electoral Commission has given National a "warning" over failing to declare a donation in time.
All political donations above $30,000 must be declared to the Electoral Commission within 10 working days, but the National Party failed to declare $35,000 in donations from businessman Garth Barfoot on time.
The return should have been filed after the election in November last year but it was not filed until March 31, which prompted the Electoral Commission to investigate.
It has written to the National Party "reinforcing the importance of adhering to the statutory timeframes" but noted that "an additional step is being taken to strengthen donation notification processes within the party".
Since 2011, the Electoral Commission says there have been 11 instances of parties filing a late return for donations over $30,000, including this one involving the National Party.
In each case the Electoral Commission looks at all the circumstances including the reason for the failure, the amount involved, when it came to light, and the party's processes for recording donations.
Unlike the National Party, the Māori Party has been referred to police for failing to declare $327,000-worth in donations, most of which came from former co-leader John Tamihere.
The Electoral Commission also revealed a second referral to police from another party - a candidate who allegedly failed to disclose donations.
It wouldn't disclose who it was - but he did it himself: Billy Te Kahika, who co-led Advance NZ.