The only donation NZ First leader Winston Peters listed was $46,422.84 from the NZ First Party - the same amount as his expenses.
That possibly indicates he followed the same process National often uses under which donors donate to the party rather than the candidate and funding is then passed on to the candidate.
Party donations have a higher $15,000 disclosure limit.
Mr Peters' expenses included $16,000 for a region-wide pamphlet drop and $7043.75 for the signage on his infamous 'Force of the North' bus.
The bus hire and driver costs do not have to be disclosed as election expenses, which covers mainly advertising spending.
The spending cap for candidates in a by election is $52,100 and Mr Osborne spent slightly more than Mr Peters at $48,817.
His costs included $1,150 to the National Party's pollster Curia Market Research for phone rental and call costs to ring around the electorate in the lead up to the byelection.
National was criticised for appearing to filter its donations through the party rather than straight to individual candidates during the last election.
Although it is within the law, it escapes the much lower disclosure thresholds for candidate donations.
Mr Peters would not say what he had told donors to do, but said both National and Labour had sent donations to the party instead of individual candidates in the past.
"I declared exactly what was required by electoral law."
He said the party had also paid for the costs of the bus and driver, although that sum was not included in his declaration of a donation from the party.
He said he did not have to declare those expenses under electoral law. He laughed when told none of his rival Mark Osborne's donations were from Northlanders.
The candidate returns also show Focus NZ candidate Joe Carr spent $2,300 on front page ads in the local papers urging voters to vote for Mr Peters instead of himself.
Those ads appeared to breach electoral laws because Mr Carr did not have Mr Peters' permission to run them.
A spokeswoman for the Electoral Commission said it had investigated the advertisements but decided not to take further action after Mr Carr explained he misinterpreted the rules and it was not 'wilful.'
In his return, Mr Carr split out the cost of the ads in question saying they cost a total of $2,288.70 - slightly more than half of Mr Carr's total advertising spending of $4,346.
Failure to get written authorisation from the candidate in question carries a $10,000 fine if the breach was not deliberate or up to $100,000 and/or up to 2 years in prison if wilful and a corrupt practice.
It would also have required Mr Peters to include some of the costs in his own expenses.
Mr Peters has previously said he did not authorise the ads and had not known Mr Carr intended to run them.
