Irish grandfather's surname misspelled

It's misspelled on his birth certificate, as well as his parents' surname. Correct on every other document. When filling in MY application do I put the misspelled name as surname on his birth certificate, and then change of name as correctly spelled. Or do I put it as misspelled without a change of name note, not do I put it as it should have been spelled? Many thanks for advice.
Sara

What application are you making? And in which country are you making the application?

I'm applying from the UK, England, for Irish citizenship, registration of birth first, through my Irish grandfather. Does that make a difference to how I fill in surname on birth certificate? Thank you

Is the misspelling a latin version of his surname? It's very common to see different spellings of surnames in Irish records because the church often use the latin version of first and second names on baptism and marriage certificates and this often then gets carried through onto civil documents. This was the case with my grandfather, and this didn't cause any problems with my foreign birth registration process.

On all forms, you should use his correctly-spelled name. The Irish authorities will be well used to seeing variations on names so they will be able to deal with it, but you could include an explanatory note to say that his correct name is X but it's been misspelled on certain documents.

Thanks for your reply. The surname on the birth certificate simply omits an S, for my grandfather and his parents. I just don't know whether to input this misspelled name where it asks for name on birth certificate, or put in the correct spelling, effectively fibbing, as on all the other certificates. I guess I just have to make a choice, and I will do a covering note, as you suggest.
Tx