No post code box for Ireland

[Littlepants]

When customers fro  Ireland try to register in my shop, there is no post code box. However, when they have filled in all the boxes, they get a message saying they must enter a post code. But they can't because there isn't a box. The only way around it that I can find is to select UK as the country, put the post code in, and THEN change the country back to Ireland. Not very helpful for new customers, as they are unlikely to discover that - I only discovered it myself by accident.

 

So how do I get the address registration page to give a post code box?

 

Any ideas please?

 

TIA