Giving feedback to someone above or below you in the hierarchy is awkward enough; giving it sideways, to a peer who can simply decide you have overstepped, is the hardest version of all. There is no authority to lean on and no formal process to hide behind, only the relationship - which is precisely why getting it right matters. Vague, badly timed feedback poisons a working relationship faster than saying nothing. Specific, well-framed feedback can deepen one.
Use the SBI model
The cleanest structure I know is Situation, Behaviour, Impact, and it works because it strips out judgement. You describe the situation ("In yesterday's client call"), then the specific behaviour you observed ("you answered the question before Priya had finished her sentence"), then the impact it had ("she went quiet for the rest of the meeting and we lost her input on the budget"). Notice what is missing - no "you always," no "you're rude," no amateur psychology about why they did it. You report what happened and what it caused, and you let the other person draw the conclusion. The discipline of sticking to observable behaviour, rather than your interpretation of their character, is what keeps the conversation survivable.
Timing and specificity decide everything
Feedback has a short shelf life. Raise it within a day or two while the detail is fresh, but never in front of an audience and never when either of you is tired or rushed. A quiet "have you got five minutes?" beats an ambush every time.
- Be specific - "the report was unclear" helps nobody, while "the summary had no recommendation, so the board didn't know what we wanted them to decide" gives them something to act on.
- Balance it; name what they did well too, as long as the praise is real and not a sandwich filler.
- Ask before you assert - "can I share something I noticed?" - because consent changes how it lands.
Then let them respond
Peer feedback is a conversation, not a verdict. Once you have said your piece, stop talking and listen, because you might be missing context that reframes the whole thing. This approach works - unless you treat it as a tactic, delivering the formula while your tone says you have already decided they are in the wrong. People hear the intent long before they parse the words.