# Non-Unique Addresses (NUAs)

When working with Irish address data through the Eircode Address Database (ECAD) or Eircode Address File (ECAF), you will frequently encounter Non-Unique Addresses (NUAs). Understanding how to correctly identify and handle these is essential for accurate address capture, validation, and delivery routing.

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## What is a Non-Unique Address (NUA)?[​](#what-is-a-non-unique-address-nua "Direct link to What is a Non-Unique Address (NUA)?")

* A Non-Unique Address (NUA) is an address that does not contain a unique building number or a unique building name.
* Ireland has a very high level of non-unique addresses.
* Approximately 35% of all Irish addresses are non-unique, which equates to 600,000 addresses nationwide.
* The typical example of NUA addressing occurs in rural areas where every address in a townland is the same.
* Because these addresses are identical, mail is delivered by the local knowledge of postal delivery personnel who know which addressee lives in which house.

## What Makes NUAs Unique?[​](#what-makes-nuas-unique "Direct link to What Makes NUAs Unique?")

* For a NUA address, it is impossible to match to a unique record in the ECAD and assign an Eircode based on the text address alone.
* Knowing the text address is simply not sufficient information to determine the Eircode.
* For example, four separate houses in a townland can have the exact same address lines but each will have a completely different Eircode.
* The API response includes a `nua` boolean field: `true` when the address is non-unique, `false` when it is unique.

### Example API Response[​](#example-api-response "Direct link to Example API Response")

The following is an ECAD response for a rural NUA property. Note the empty `building_name`, `building_number`, and `primary_thoroughfare` fields — this address has no distinguishing text elements. The `nua: true` flag confirms it shares its address lines with other properties in the townland.

```
{

  "id": "ecad_1234567890|en",

  "dataset": "ecad",

  "ecad_id": "1234567890",

  "language": "en",

  "department": "",

  "organisation": "",

  "sub_building_name": "",

  "building_name": "",

  "building_number": "",

  "building_group": "",

  "primary_thoroughfare": "",

  "secondary_thoroughfare": "",

  "primary_locality": "Example Townland",

  "secondary_locality": "Nearby Village",

  "tertiary_locality": "County Name",

  "post_county": "County Name",

  "eircode": "A00 B1C2",

  "line_1": "Example Townland",

  "line_2": "Nearby Village",

  "line_3": "County Name",

  "line_4": "A00 B1C2",

  "nua": true,

  "address_type": "Residential Address Point",

  "building_address_type": "Single Occupancy Residential Building",

  "primary_locality_address_type": "Rural Locality",

  "secondary_locality_address_type": "Rural Locality",

  "building_type": "Detached",

  "building_use": "R",

  "longitude": -7.123456,

  "latitude": 53.123456,

  "country": "Ireland",

  "country_iso": "IRL",

  "country_iso_2": "IE"

}
```

Key fields to note:

* **`nua`** — `true` indicates this is a non-unique address
* **`eircode`** — the only reliable way to distinguish this property from its neighbours
* **`longitude` / `latitude`** — precise coordinates for delivery routing
* **`address_point_id` / `ecad_id`** — stable identifiers for the specific property

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## Best Practices for Handling NUAs[​](#best-practices-for-handling-nuas "Direct link to Best Practices for Handling NUAs")

### 1. Make the Eircode the Primary Identifier[​](#1-make-the-eircode-the-primary-identifier "Direct link to 1. Make the Eircode the Primary Identifier")

* Traditional text deduplication will fail for 35% of Irish addresses. Use the Eircode (or ECAD identifiers like `ecad_id` or `address_reference`) to uniquely identify the property.
* Never rely on `line_1` through `line_3` as unique database constraints for Irish addresses.

### 2. Guide the User Experience[​](#2-guide-the-user-experience "Direct link to 2. Guide the User Experience")

* A search for an NUA townland will return multiple identical address strings.
* Your UI should prompt the user to provide their Eircode to distinguish their specific property from their neighbours.

### 3. Verification Logic[​](#3-verification-logic "Direct link to 3. Verification Logic")

* **If `nua` is `true`**: The text address lines are shared. The Eircode is strictly required to differentiate this specific property.
* **If `nua` is `false`**: The text address lines (e.g., building number and street) are sufficient to uniquely identify the property.

### 4. Use Geographic Coordinates for Routing[​](#4-use-geographic-coordinates-for-routing "Direct link to 4. Use Geographic Coordinates for Routing")

* Because NUAs lack street names or building numbers, delivery routing by text alone is practically impossible without local knowledge.
* Each ECAD address includes `longitude` and `latitude` coordinates, allowing you to pinpoint the exact building for delivery or mapping purposes.