The phrase "follow up on" trips up writers because it has a near-twin: "follow up with." Both appear constantly in business email, but they aren't interchangeable. Get the distinction right and your message reads cleanly. Muddle them and your reader, even briefly, has to work out what you mean.
The core difference: things vs. people
The preposition does real work here. "Follow up on" points at a subject, a task, or a matter. "Follow up with" points at a person or an organisation.
- Follow up on something: "I'll follow up on the invoice." / "She followed up on the complaint."
- Follow up with someone: "I'll follow up with the vendor." / "He followed up with the hiring manager."
If you're not sure which to use, ask yourself: is the object of the sentence a topic or a person? Topic gets "on." Person gets "with." That test works in every case.
The verb, the noun, and the adjective: spelling matters
"Follow up" is two words when it's a verb. It becomes one hyphenated word when it's a noun or an adjective. This is one of the most common spelling errors in professional email.
Correct: "I need to follow up on this." (verb, two words)
Correct: "Send a follow-up email." (adjective, hyphenated)
Correct: "Schedule a follow-up." (noun, hyphenated)
Wrong: "I need to followup on this." No version of the word works as one unhyphenated string.
This parallels the way other compound expressions work in English. If you've ever wrestled with whether a modifier needs a hyphen, the same logic applies here: modifiers before a noun get hyphenated, standalone verbs don't. For a deeper look at how hyphens work with compound modifiers, the post on "a well-known problem": is it hyphenated or not? covers the underlying rule clearly.
Common sentences, done right
Here are the constructions that show up most often in business writing, with the correct form in each case.
"I wanted to follow up on my previous email." Correct. "My previous email" is a thing, not a person, so "on" is right.
"I'm following up on our conversation from Tuesday." Correct. The conversation is the subject matter being revisited.
"Please follow up with Sarah before the end of day." Correct. Sarah is a person.
"I'll follow up with the supplier regarding shipping." Correct. The supplier is an organisation. "Regarding shipping" names the subject matter, but the direct object of "with" is still the supplier.
"I'm just following up." Also correct. When the context is already clear, dropping the preposition entirely is fine and often more direct.
When "follow up on" sounds wrong
The phrase starts to sound strained when writers use it to mean "check on a person." Consider: "I'll follow up on John." That sentence works, but it distances you from John. It treats John as a task on a list rather than a person in a conversation. "I'll follow up with John" is warmer and more natural in most professional contexts.
Use "follow up on John" only when John genuinely is a to-do item in someone else's system. A manager telling an assistant "follow up on John's application" is using the phrase correctly: the application, not John, is the matter being tracked.
In email closings
Follow-up phrases appear most often at the end of business emails. Two closings cause the most confusion.
First: "I'll follow up on this by Friday." Clean and direct. The reader knows a task is being tracked and when to expect movement.
Second: "Please don't hesitate to follow up with me." This works, but it's wordier than it needs to be. "Feel free to reach out" or simply "Let me know if you have questions" often serves the same purpose with less friction. Speaking of which, the advice in how to invite inquiries in business writing covers exactly when and how to phrase those closes effectively.
One more thing worth knowing: "I will follow-up with you shortly" is wrong. The hyphen belongs to the noun and adjective forms only. As a verb, it stays as two separate words: "I will follow up with you shortly."
A note on tone
How you frame a follow-up matters as much as whether you spell it correctly. "Just following up" reads as apologetic in many contexts. "Following up on the proposal I sent Monday" is more confident because it grounds the message in a specific, shared reference point.
Business writing rewards specificity. Name the thing you're following up on rather than leaving the recipient to guess. That one habit makes follow-up emails shorter, clearer, and far more likely to get a response. For the same reason, the opening line of any follow-up carries weight: what actually works in opening sentences applies directly to follow-up messages, not just first-contact emails.
Get the preposition right, spell the compound correctly, and say exactly what you're tracking. That's the whole rule.