According to Arizona tax records, the mayor's primary residence has been a Scottsdale home since 2013.
Katz purchased the 4,400-square-foot home from the sister-in-law of property developer Sandy Shindleman in 2012.
The sale price was not disclosed on the title transfer, but Katz has said he paid more than $1 million US for the property.
Files from the Maricopa County Assessor's Office list the home, worth $934,000 US, as Katz's primary residence.
According to the Arizona Department of Revenue, a primary residence must be the "one and only main residence where you intend to reside more than nine months of the year … you can have only one primary residence no matter how many homes you own."
A home cannot be listed as a primary residence if the owner uses it as a vacation property, according to the rules.
Mayor's office says it's a mistake
A spokesperson with Katz's office said on Monday that an error must have led to Katz’s Arizona property being listed as his primary residence.
Katz declared himself a Canadian citizen living in Winnipeg to the property titles company in Arizona when he registered ownership of the Arizona home, the spokesperson said, adding the mayor does not plan to move there permanently.
The mayor was not available for an interview on Tuesday.
According to the Maricopa County Assessor's Office, the home was originally designated as "owner occupied," but state laws changed in 2013 and the house was reclassified as a "primary residence."
That change would give Katz a $600 tax credit over two years.
Robert Pizorno, a spokesman with the assessor's office, told CBC News that notices were sent to Katz, giving him an opportunity to change the classification of the home. However, officials never heard back from him.
Pizorno said the county assessor's office has reached out to Katz's office to "expedite correcting this problem and will work with him to accomplish this quickly."
When asked if Katz would have to pay back the tax credit, Pizorno said that's up to the county treasurer to decide.
"All we have authority over is the legal classification so we are going to work with him to get our form filled out correcting that issue," he stated in a subsequent email.
"Our County Treasurer is responsible for the tax credit and they are aware of this situation and it’s up to them whether they will pursue recovering the funds."
Critics, observers weigh in
Chris Adams, a political watcher based in Winnipeg, said Katz has been dogged about his Arizona home for some time.
"A lot of people were concerned that the mayor wasn't as devoted to spending as much time as he could have as mayor in the city," Adams said.
"To read reports that Arizona is declared as his primary residence, I think, will frustrate a lot of observers and a lot of citizens."
Even if the latest controversy stems from an error, a municipal ethics commissioner could rule on such matters — that is, if such a position exists at the City of Winnipeg, said Coun. Jenny Gerbasi.
The position does not exist, despite numerous motions calling for one to be created.
"I definitely think it would be helpful to have that office for lots of reasons, so when there are questions like this there's somebody to investigate, there's a process for having sanctions and accountability for things that do happen," Gerbasi said.
Maricopa County Assessor's Office statement
Below is the full statement from Robert Pizorno, of the Maricopa County Assessor's Office in Arizona. The statement was sent to CBC News on Tuesday afternoon:
"In Aug. of 2012, a Special Warranty Deed was filed and recorded in Maricopa County, transferring a residence from Terri Nordstrom to Sam Katz, which is listed as 18039 N. 99th St., Scottsdale, Arizona 85255. The Deed listed this address as both the situs address and the mailing address. In 2012, the property was classified as Owner Occupied, per state statute. In 2013, the law changed and the property was reclassified as Primary Residence from an Owner Occupied classification, pursuant to the legislative changes at the state.
"During this time period, four notices were sent to Mr. Katz — 2 Notices of Valuation and 2 Taxation notices. In the 2 Notices of Valuation, the property was clearly identified as a Primary Residence. In the 2 Taxation notices, the property was clearly shown as receiving a tax credit of $600 for each of the years in question, for being a primary residence. Each of these notices gave the owner the opportunity to correct the classification of the property, which is required pursuant to ARS 42-12004 and ARS 33-1902, to a class 4 property instead of a class 3 property.
"Currently, we have reached out to Mr. Katz’s office to expedite correcting this problem and will work with him to accomplish this quickly."