In my North American flavor of English, the phrase “so it is” is used as as standalone response to express mild to medium amounts of surprise at something not shocking. For example, if I thought it was Monday but someone pointed out that it was still Sunday, the conversation might go a bit like this:
S: ugh I don't want to go to work.
K: it's Sunday, you don't have to
S: It's not Monday?
K: no it's Sunday.
S: *looks at the phone* so it is!
In Irish English – or Hiberno English depending on your terminological preference- the phrase has a different use. Called variously the Hiberno-English emphatic tag, a vocalized pause, or postpositional phrasal emphasis, “so it is” serves to both emphasize information and intensify actions.
Examples:
- Young urban people have been known to shun even the music, and that is some fine music so it is.
- It’s raining , so it is
Though “so it is” comprises the largest amount of this emphatic structure, other verbs are involved as well, including “have” and do”.
- I like a cup of tea at night, so I do
- I’m from Derry, so I am.
- I’ve finished writing, so I have.
Past tense verbs also get the emphatic tag treatment, and occasionally future forms do as well, though that’s less common.
- They lost, so they did.
- We were ill, so we were.
- They’ll do the work with very little training, so they will.
Though not all varieties of Irish English employ this feature equally, Ulster English being its prime stomping grounds- the emphatic tag is certainly a marker of the genre that conveys significant meaning for people. Many speakers who use it say they they would feel uncomfortable ending the same sentences without the tag.
And even if you don’t use the form yourself, in can come in handy. For example, if you truly want to stump someone who has yet to be initiated into the glory of Irish English, just say to them “It’s quare bad, so it is.” This is a particularly good approach if you wish to get out of talking to a person at a social event. They will be standing there in a frozen stupor unable to parse what was said and whether it was bad or good, so you will be able to escape immediately, so you will.