Replyku

Formal or casual? Getting the register of a reply right

5 min readUpdated

Most replies that land badly aren't wrong in content — they're pitched at the wrong distance. Here's how to read the register and match it.

The same sentence can be perfect or absurd depending on where it lands. "Dear Mr Prasetyo, I hope this email finds you well" is unremarkable in a first approach to a supplier and faintly alarming as a WhatsApp reply to a colleague you sat next to yesterday.

The good news is that you rarely have to guess. The message you received is a specification for the reply, and reading it takes about ten seconds.

What to read in the incoming message

  • The greeting. "Dear" and a surname sets one distance; a first name sets another; no greeting at all sets a third.
  • Sentence length and punctuation. Full stops and capitals signal a considered message; lowercase and missing punctuation signal speed.
  • The sign-off, or its absence. "Kind regards" and a signature block is a different medium from a message that just ends.
  • Whether they used contractions. "I'd" and "can't" are a licence to be informal; "I would" and "cannot" are not.
  • The channel. Email tolerates formality that chat does not, whatever the words.

Match, don't exceed. Being one notch more formal than the person who wrote to you reads as polite distance. Being two notches more formal reads as displeasure, and people notice it immediately.

The same reply at three distances

Here is one piece of news — a delay of a week — written for three different recipients. The information is identical; nothing else is.

Formal: a client you have never met
Dear Ms Wibowo, Could you confirm whether the audit report will be delivered by the 30th as scheduled? Kind regards, Daniel Prakoso
Dear Mr Prakoso, Thank you for checking. The report will be a week later than planned — 7 October rather than the 30th — because two of the branch submissions arrived incomplete and had to be requested again. The fieldwork itself is finished, and nothing in the findings changes as a result of the delay. If the 30th is a hard date on your side, please let me know and I will send the completed sections in draft so you are not waiting on the full document. Kind regards, Sinta Wibowo
Neutral: a colleague in another team
Hi Sinta — is the audit report still on track for the 30th? Need to know for the board pack.
Hi — it's slipping to the 7th, sorry. Two branches sent incomplete submissions and we had to go back for them. Fieldwork is done and the findings aren't affected, so it's genuinely just the write-up. If the board pack can't move, I can give you the finished sections in draft this week. Let me know which you'd rather have.
Casual: someone you work with daily
audit report still landing on the 30th?
nope, 7th — two branches sent junk and we had to chase them again fieldwork's done, findings unchanged, it's just writing now yell if the 30th is hard and I'll send you the finished bits early

Formality in Indonesian is a different problem

In English, register is mostly a matter of contractions and greeting. In Indonesian it is grammatical, and choosing wrong is more visible: aku/kamu against saya/Anda, whether you use Bapak or Ibu with the name, and whether the sentence keeps its full prefixes and suffixes or drops into everyday clipped forms.

  • Saya + Bapak/Ibu with a surname: the default for anyone senior, external, or unknown. Nobody has ever been offended by it.
  • Saya + Mas/Mbak with a first name: the working middle ground with peers and near-peers.
  • Aku + kamu: friends, and colleagues who have already used it with you first.
  • Whoever is senior sets the register. Follow their lead, and don't downshift before they do.
  • Sudah/belum, not udah/belum, in anything written to a client. The clipped forms read as chat wherever they appear.

Three things that break register

  • A formal template pasted into a chat app. The greeting alone announces it wasn't written for the person reading it.
  • Corporate abstraction in a personal message — "circle back", "align on", "per my last email" in a note to one person.
  • Excessive apology in a professional reply. It reads as junior, and it invites the reader to think something went wrong.

If you genuinely cannot tell how formal to be, write the neutral version: full sentences, first names, no template greeting, no slang. It is never the wrong answer, only occasionally the dull one.