According to the leaked audit, UKIP broke EU spending rules by spending money on polling during its general election campaign in 2015 and ahead of the EU referendum.
Business Insider has contacted UKIP for comment and will update when we hear back.
UKIP receives money from the EU as a member of "Alliance for Direct Democracy," (ADDE) a political grouping in the European Parliament where UKIP has several representatives. The money is meant to be spent on funding to promote the EU.
European Parliament rules prohibit the "indirect financing of a national political party" and funding "a referendum campaign."
The report says, according to Sky News: "The constituencies selected for many of the polls underline that the polling were conducted in the interest of UKIP."
"Most of the constituencies can be identified as being essential for reaching a significant representation in the House of Commons from the 2015 General Election or for a positive result for the 'Leave campaign'."
Rerferring to the EU referendum, it said: "Several pollings can be considered as financing of a referendum campaign which violates 8(4) ... prohibiting the financing of referenda campaigns."
The audit puts the total misspend at £430,000 ($537,000), although some of that was misspent by other parties within ADDE, the audit said UKIP was responsible for the "lion's share."