The most important thing to remember is that there is no such form as it’s’. Its is one of a few words that are already possessives, and do not, therefore, need an apostrophe adding to them. These words are

my/mine its

your/yours our/ours his their/theirs

her/hers whose

As we noted in the last passage, it’s is two words (‘it is’ or ‘it has’) contracted into one: it has nothing to do with the possessive. It’s is used in a large number of situations, but it is by far the best policy to avoid contractions (words such as can’t, don’t and won’t) in formal essays, as these are colloquial forms of the words and therefore not entirely appropriate. Some writers, it has to be said, disagree. There is, though, a further danger with contractions: if you forget to put the apostrophe in, for example, ‘can’t', you end up writing ‘cant’.

We hope by now, therefore, that you can see the sense of avoiding writing it’s and instead using it is whenever possible:

It is my dog and ... Read more...