Two sentences that mean exactly the same thing.
"I would like to discuss the timeline."
"I'd like to discuss the timeline."
The first one is more careful. It is also the one that makes a client wonder what is wrong.
This is a strange piece of English and almost nobody is taught it, so people who write carefully often get it exactly backwards. The more effort you put into sounding correct, the colder you sound.
What contractions actually signal
Contractions are not shortcuts. They carry information about register, which is the level of formality a piece of language is operating at.
Spoken English contracts by default. Nobody says "I would like to" in conversation unless they are emphasising the word would, or they are in a courtroom, or they are furious. Written English contracts too, in anything informal.
So the uncontracted form is marked. It signals one of a small number of things: a legal document, a very senior stranger, deliberate emphasis, or displeasure.
When you write "I would like to discuss the timeline" to someone you normally chat with about their weekend, you have selected the register used for contracts and complaints. The client cannot articulate that, but they feel the temperature drop.
Why careful writers fall into it
Here is the trap. Formality feels like respect. If you are writing to someone important, or writing about something that makes you nervous, the instinct is to write more carefully, and more carefully means more formally.
Non-native writers get hit hardest by this, and it is genuinely unfair, because it happens for a good reason. Formal English is what gets taught. Textbook English does not contract. Exam English does not contract. Then you write to a client in the most correct English you have and it reads as stiff, which is the opposite of what you were going for.
I did this for years. My most careful emails were my coldest ones, and I could not understand why the messages I dashed off got warmer replies than the ones I laboured over.
Where the effect is strongest
Length matters enormously here.
In a long document, formal register is fine. Nobody reads a proposal and thinks the writer is annoyed, because a proposal is supposed to be formal and there is enough text for tone to average out.
In a three-line message, there is nowhere for tone to hide. Every word is load-bearing. A short formal message is the exact shape of a message from someone who is being professional at you, and everyone recognises it, because it is what people write when they are unhappy.
Short and formal is the dangerous combination. Watch for it specifically.
The ones that do the most damage
I would like to. Covered above. Use I'd.
I am writing to. This is pure letter-writing convention from an era of physical mail and it announces distance immediately. Delete the whole phrase and start with the point.
Do not hesitate to contact me. Nobody has said this out loud since about 1974. "Let me know if anything is unclear" does the same work.
I would be grateful if you could. Grateful is a large word for a small request. It either reads as formal to the point of coldness or, if the client knows you well, as faintly sarcastic.
Please be advised that. Insurance letter. Nothing good follows it.
The exception, which matters
There are moments when the uncontracted form is the right choice, and it is worth knowing them so you can use the effect deliberately instead of accidentally.
Emphasis. "I did not agree to that" is stronger than "I didn't agree to that," and sometimes that is precisely what you want. The formality gives it weight.
Genuine first contact with someone senior, where a small amount of distance is appropriate and expected.
Anything that might be read later by a third party, like a scope dispute or a contract discussion. Here the legalistic register is doing real work.
The rest of the time, contract.
Read it out loud
This is the only test that reliably works, and it takes four seconds.
Read your message aloud in the voice you would use if the client were sitting across a table. Anywhere you would not naturally say the words that way, you have drifted into a register you did not intend.
You will find yourself saying "I'd" and "we're" and "that's" without thinking about it, because that is how you speak. Then you look at what you wrote and it says "I would" and "we are" and "that is," and you can see the gap.
How far to go depends on the person. I have one client who writes in full sentences with formal sign-offs and would find casual contractions jarring, and another who sends me voice notes. Matching them is the actual skill, and it is the thing I eventually got tired of tracking by hand across a dozen relationships.
But the default should be the way you talk. Formality is a tool, not a safety net.