The TAT and TMK Numbers on a Ko Olina Villa Page: What They Mean

Scroll down any villa page on this site and you will see two lines that look like paperwork: a Hawaii TAT number and a TMK. They are easy to skip, but they tell you something useful about the villa and the person you are booking with. Here is what each one means, in plain English.

The Hawaii TAT number

TAT stands for Hawaii's transient accommodations tax. The state Department of Taxation treats a place rented to a visitor for less than 180 consecutive days as a transient accommodation, and the person who furnishes it is the "operator." When a villa owner uses a manager, the department's guidance says the owner of the unit is still the operator.

Each operator registers with the state and receives a registration number. The department notes that this is "also commonly referred to as the transient accommodations tax license number." On our villa pages these numbers appear in the form TA- followed by digits.

Why the TAT number shows up in ads

The Department of Taxation's guidance for operators says an advertisement for a transient accommodation must include the operator's registration identification number, or an electronic link to it. The department is clear that an advertisement can be online, including a posting on a website, social media account or blog.

The same guidance says the certificate of registration (or a notice of where to view it) and the local contact's details must be displayed at the rental, conspicuously, not in a hard-to-find spot.

The state does pay attention to this. In October 2025, Hawai'i Public Radio reported on a legal notice listing 18 people or entities that had not shown their tax information in their rental ads. An official with the Department of Taxation's special enforcement division described the rule as one that "requires people to display their tax registration numbers."

For you as a guest, the TAT number simply shows which registered operator the listing belongs to.

The local contact

The guidance also covers who you can reach on the island. An ad must include the name, phone number and email of a local contact unless the guest gets that contact's details before the stay. A local contact is defined as "an individual residing on the same island as the transient accommodation," or a qualifying business on that island. Each villa page here names its on-island agent.

The TMK

TMK stands for tax map key. The state's Oahu parcel data describes tax parcels (TMKs) as divisions of property "for the purpose of assessment by Real Property." The city's real property pages use "parcel ID" and "TMK" for the same thing, and when a building is divided into separate units, the office assigns each unit its own parcel ID number.

In that parcel data, the TMK starts with a county code (the first digit), followed by numbers that place the parcel on the tax maps. You do not need to decode it. What matters is that each villa page lists a TMK, which ties the villa to its own unit-level parcel number.

How to use these numbers before you book

• Look for both lines on the villa page: Hawaii TAT and TMK.
• Note the on-island agent named on the page, so you know who is local.
• Ask the host any questions directly; every request goes to the villa's owner or on-island agent.

Stays start at 6 nights, and groups of up to 150 can stay across several villas at the same resort.

This is general information from the Department of Taxation's published guidance, not legal or tax advice.

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