Immigration investigators are looking into a large Auckland private tertiarty institute "for issuing receipts containing false or misleading information".
Receipts issued by the International College of Auckland on Queen Street showed students paid more in tuition fees than they actually had. For example, one receipt showed a payment of $6000 when just $4000 was paid.
The college then got students to sign up and make part payments of the remaining fees over the duration of their course.
"This appears to be a serious breach of [Immigration New Zealand] requirements," the Qualifications Authority, which uncovered it, said.
Immigration New Zealand warned students from the college last week that they could lose out on getting new visas for failing the good-character requirements if they were found to supply false or misleading information in the receipts.
"INZ takes matters of immigration fraud very seriously and conducts robust assessment of all applications," Immigration NZ said in a statement.
"As the investigation is still under way we are unable to comment any further."
The college, which has more than 600 students, is already in trouble with NZQA over plagiarism and written English work done by students described as incomprehensible.
It has now voluntarily shut down four of its business courses, and 80 students enrolled in those courses will have to restart their studies at another separate college, Aspire 2.
Immigration NZ would not say how many students were caught up in the receipt investigation.
In the past, the department has been criticised by student advocates for being quick to target students over fraudulent visa documents, for instance by deporting them, while taking little or no action against the private training establishments (PTEs) involved, or their marketing managers.
Immigration NZ refused to comment on how its current investigation targeted the college itself.
"We have already apologised to NZQA for the issues that they found with our financial management during our last evaluation," college principal James Zhu said in an email.
"We ensure that this will never happen again."
He declined to be interviewed, but said the college would cooperate with Immigration NZ's investigation.
Where any PTE breached the rules, NZQA said "firm action" was taken to ensure the integrity of New Zealand qualifications and the tertiary education sector.
In an evaluation report last month, NZQA said it was "not yet confident" in either the college's educational performance or self-assessment.
The same report also found the college had been collecting fees from some students before they had actually begun studies, breaching student fee protection rules.
NZQA said the college had since fixed this and put the funds back in the Public Trust where it had been held.