Most non-native English speakers frequently (and mistakenly) use Its and It's interchangeably in IELTS writing tasks 1 & 2. Here are the appropriate governing rules for using its vs it's. Make sure you use them correctly in IELTS, especially in writing tasks.
It's vs Its.
"Its" is the possessive form of the pronoun it. This is unique because usually an apostrophe is needed to show possession. For example. "The cat was chasing its tail." It's is the contraction for "it is" or "it has." For example. "It's Mike's birthday today."
NOTE: Its' is NEVER correct. 
