As a verb, flag means to highlight something, typically a risk, error, or concern. Two prepositions guide the word choice. Use to for the recipient and for for the purpose. The word usually has a neutral-to-negative tone, so you flag problems and mismatches, not achievements.
Recipient-directed: flag something to someone
The main pattern is flag [an issue/risk] to [someone], but you can also simply flag a concern.
"Please flag any discrepancies in the quarterly report to the compliance team immediately."
"We should flag this potential risk to the steering committee."
"To" introduces the person or team that receives the alert. The issue is the object being flagged, while the recipient follows "to."
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See how Lyra Practice works →Purpose-directed: flag something for review
The second pattern says what should happen next: use flag [something] for [review/attention]. A related phrasal form is flag up [a concern].
"We need to flag the inconsistent data entries for immediate investigation."
"For" goes with the needed action, not a person. You flag data for investigation, not to investigation.
Systems and compounds: red-flag, automated flagging
Flag also appears as a compound verb, and automated systems can flag things too. Common forms include red-flag a transaction and be red-flagged by [the system].
"Our new compliance software is designed to monitor all outgoing payments. The system will automatically flag any transaction that matches criteria on the international sanctions list, preventing it from being processed until an officer clears it."
What doesn't pair with flag
Three mistakes commonly appear in professional writing. "Flag down an idea" uses the wrong phrase because "flag down" means calling a taxi or stopping someone in the street. For ideas, use "flag up" or just "flag." "Flag about a problem" adds an unnecessary word. Flag takes the problem as its direct object, not "about" it. Finally, "flag the steering committee for this risk" reverses the order. At work, you flag the issue to people, not the people themselves.
Practice scenarios
Practice using flag in these situations.
- making sure a backend team's slipping milestone is visible on the project dashboard
- marking an unusually high invoice for a second look from senior accounting
- flagging an important action item buried in a long client email so it isn't missed
Try these useful practice phrases.
- "I want to flag [issue] to [person/team]."
- "Can you flag this for review?"
- "The system automatically flags [criteria] for [action]."
Flag sounds natural when it points to a risk, not an achievement, and directs that risk toward someone who can act. Keep the two prepositions clear: to the person and for the purpose. Then it reads like a normal business term.
Lyra Practice helps advanced non-native English professionals learn the nuance of high-value workplace expressions and practice using them in realistic scenarios, so their English sounds natural, precise, and senior at work. Try Lyra Practice.