Como dizer "Faltou fazer..." em inglês

It´s lacking the ring.
You forgot the ring.
It seems like you forgot the ring.

The last one softens the statement, it´s good not to seem rude.
On the other hand, Lois P. Frankel (author of the book Nice Girls Still Don´t get the Corner Office) would say that it weakens it. By this reasoning, it would seem like you are making a tentatively affirmation, not much confident. So, it goes with the setting and the message one tries to convey, and the audience as well.

Ah, my suggestions were like you was saying/pointing out that to someone else.
If it´s you saying about your own job/plan/task etc, these ones would do:
It´s lacking the ring.
What I need to do next is the ring.

You wouldn´t say that "you forgot" in such case, it would work against you (and the perceived professionalism of yours.)

It's not a professional context, I'm talking about a personal experience, in which my boyfriend and I planned a lot of things, but one we couldn't do, and it was the "tatto ring". We did everything, except the ring. I thank you both, but I think the suggestion from Telma is more appropriate.
Thank you so much!

Mais uma:

"I still have to tattoo the ring (on-obviously-his ring finger)"

Outra:

I have yet to tattoo the (wedding) ring.

Yes, Jessica, I agreed.