Should I put tags for things that haven't happened yet but will in future chapters?

Hello, I've recently begun experimenting with posting my stories from other sites to AO3 and have a question about tagging.

I have a series with eight chapters, but I have only posted the first three to the site. Should I wait to put tags for those upcoming chapters, or put them now?

For example, chapter 7 involves anal sex, but none of the chapters before it even mention anal. Would putting a tag for it be like false advertising since it isn't actually in the story yet?