In English, some kind of determiner or quantifier is almost always required (except with proper nouns, plural nouns, and "uncountable" nouns). In this case any of the following would complete the sentence:
The current plan
My current plan
This current plan
Every current plan
and many others. The only time "current plan" would not take a determiner is if it was the name of something, like a movie:
I see that "Current Plan" is playing at the local theater.
I understand that this may seem excessive to non-English speakers, but nevertheless this is how the language works.
More about using articles before nouns
Edit: There are many special cases in English, like with labels, technical descriptions, newspaper headlines, and other "abbreviated" forms of English, where the article is routinely omitted. Your sentence is not one of these, since it sounds like something you wrote as a business memo, but as an example in a headline:
"Current Plan Insufficient" Says Mayor
Articles are also often omitted in informal conversation like in email or texts.
Hey what u think of current plan?