いいです vs もいいです

Hi all,

I'm writing because I have a doubt about the form "Can I …?" (am I allowed to…?) that I usually make with the verb in its て form plus いいですか, because sometimes I have found written the verb in its て form plus もいいですか.

I mean for example "Can I go?" that I always translate as 行っていいですか but that sometimes I find as 行ってもいいですか.

So there's this も before いい that I don't understand what does it mean, and I have the idea that it's the same form, but probably I'm missing something important.

Can someone help me? Thanks!!