It doesn't matter It does not... You would not say "It do not matter.", so it's contracted form "It don't matter" is also wrong, grammatically. You will hear it in less formal spoken English at times, though.

'It doesn't matter' is correct.

it doesn't matter of course :) as I know, "he/she/it" are followed by "does/was/is" while "you/we/they" are followed by "are/do/were" and "I" is followed by "am/do/was" except in conditional if. In conditional if, "I" usually followed by "were" :D

fdmaxey is correct. It doesn't matter is always correct. When he says you may hear it in 'less formal' English he is being kind. If you say 'it don't matter' to anyone with an education you will look ignorant.

"do" is for I/you/we//they, while "does" is for he/she/it. so the correct one is it doesn't matter.