The Republic of Ireland finally joined the 21st century today when we became one of the last developed countries in the world to adopt an official postcode system.

The Eircode system has been almost a decade in the making an has so far cost a whopping €27 million to roll out across 2.2 million homes and businesses across the Republic.

Here's all you need to know so far…

Why do we need Eircodes?
An Eircode is a unique postal identifier given to a house or building to make it easier to locate. This might not seem important if you live in a housing estate or have a numbered house, but if you live in a more rural area where your postman has to rely on your surname or townland to find your house, it will be a hugely helpful change.

Okay, and what does an Eircode look like?
Each Eircode is made up of seven characters,a mix of letters and numbers. The first three characters are based on your postal area (eg. North Dublin, West Cork) and are not unique. The last four, your Unique Identifier, apply only to your house or business. Here's the Eircode for Áras an Uachtaráin, if you fancy sending a letter to Michael D.

How do I find out mine? Do I need to apply?
Letters will be sent to each home or business over the next two weeks to let residents know what their Eircode is. The letter will also contain a pop-out card so that you can have your code handy at all times if you're likely to forget it. You do not need to apply or register, the code will come to you.

If you're curious and want to find out your code today, check out the Eircode finder here.

Does every house or business have a code?
Around 2.2 million homes and business have been granted a code, and the government says this includes "generally all postal addresses that currently receive mail." However not every single home has a code just yet, and due to Irish placenames, some addresses are currently inaccurate or missing from the system.

If I don't include an Eircode on a letter will it still arrive?
Yes, the Eircode system is still optional. In fact, some multi-national courier firms like FedEx and DHL say they will not adopt the Eircode system because of its design. They say that the Eircode offers the longitude and latitude of a residence/business but that this information has been available in the postal system for many years.

Do I have to change my address?
No, all you need to do if you want to use the code is to add it onto the end of your address, after the county (or country if you're posting a letter home from abroad).

Any chance my Eircode might be something gas like B00B1E5?
No, sadly certain characters have been removed from the system or will not appear next to each other to avoid "visual or verbal confusion." Boooo.