Learn Italian: Il direttore deve smentire un tale resoconto.

No, you can use tale with or without the indefinite article to mean "such a" before a noun. un tale resoconto and tale resoconto are both grammatically correct and mean "such a report." Using un just slightly emphasizes the singular nature, reading like "a report of this kind."

Could un tale in this sentence also mean "a certain" instead of "such a"?

Yes, depending on the context, un tale can also mean "a certain" (referring to a specific but unnamed thing or person). Without more context, this sentence could mean the director must deny "a certain report" (one we vaguely mentioned) or "such a report" (a report of this particular nature). The translation "such a" is usually the safest assumption when reacting to something.

Why use smentire instead of negare for "to deny"?

negare is the general verb for "to deny" (such as denying an accusation or denying that you did something). smentire, however, is specifically used for public refutations—meaning to officially deny a rumor, piece of news, or statement. Since the object here is a resoconto (report or account), smentire is the perfect professional verb to use.

Can I put tale after the noun, saying un resoconto tale?

No. When tale is used as an indefinite adjective to mean "such a" or "a certain", it almost always goes directly before the noun it modifies. Placing it after the noun sounds unnatural in this context.