They do that to get a value figure without paying an appraiser because it's cheaper.Be careful when reading auditor websites.

Is it really a duplex in the eyes of the auditor?

You can also check the auditor site and get an exact figure for property taxes.

Most county auditor/assessors offices offer website to search. 

Our Cuyahoga County tax rates have been updated to reflect 2019 rates (paid in 2020), you can now view the updated tax rates here and on the county auditor's website.A good reminder for those who have yet to purchase property in the Cleveland area - property taxes rarely ever stay the same and the tax figures you see on the MLS and online listings are just about useless for underwriting.

@Andrew CaldieraroMost county auditor/assessor offices have online property record data.

In either case, an assessment is done every 3 years by the auditors and property values readjust accordingly. 

Prior years have been upbeat and best characterized by Anita's commitment to keep the Auditor's staff approachable, accessible, and friendly.

I have noticed that when a bank(for example) buys a property at a sheriffs auction it doesn't get recorded on the auditors side until it get resold to an investor or other buyer.

I know in Cincinnati, the auditor's office has a specific form that needs completed to contest taxes and even offers specific evidence you can use to contest them.The easiest way in my experience is if you just bought the property for less than the assessed value, that is your evidence, since it was a recent arms length transaction.Alternatively, hiring an appraiser and full appraisal report is commonly accepted.