Starting a sentence with "but" is okay. It always has been. The prohibition most of us absorbed in school was a classroom convention designed to stop children from writing fragments, not a grammatical law. Professional writers use "but," "and," "or," and "so" at the start of sentences every day, and the results are often sharper, not sloppier, than the alternatives.
Where the "rule" actually came from
No major style guide bans opening sentences with coordinating conjunctions. Fowler's Modern English Usage, the Chicago Manual of Style, and the AP Stylebook all permit it. The Chicago Manual of Style puts it plainly: the idea that "and" and "but" can't begin a sentence is a superstition, not a rule.
Teachers discouraged the practice because students overused it. A paragraph that opens every sentence with "And" or "But" is weak writing. The solution, though, is moderation, not prohibition. Banning the construction entirely is like banning short sentences because a student wrote one that was a fragment.
The confusion stuck because it got conflated with a real rule: don't write sentence fragments. "But not today." is a fragment. "But the meeting ran late and we missed the call" is a complete sentence. One is a problem; the other is a style choice.
Why "but" at the start of a sentence works well
Opening with "but" signals a pivot. It tells the reader: what follows contradicts or qualifies what came before. That's useful information, delivered immediately, before the reader has to work through the whole sentence to find the turn.
Compare these two versions:
- "The proposal was thorough and well-researched; however, the budget figure on page four is incorrect."
- "The proposal was thorough and well-researched. But the budget figure on page four is incorrect."
The second version punches harder. The period creates a pause. The "but" at the start of the next sentence lands with weight. In business writing, where you often need to deliver unwelcome information efficiently, that rhythm is a tool worth keeping.
"However" and "nevertheless" are the formal alternatives most writers reach for. They aren't wrong, but they add syllables without adding meaning. When you're writing to a busy colleague or a senior stakeholder, a short word at the start of a short sentence usually works better than a longer connector buried in the middle of a longer one.
When it's fine to start with "but"
The construction fits naturally in most business writing contexts: emails, reports, proposals, presentations, and internal messages. It reads well when the preceding sentence makes a positive claim and the next one introduces a limitation, correction, or complication. It also works for emphasis. A single-sentence paragraph beginning with "but" isolates a point and makes it impossible to miss.
Consider the difference in tone between these two paragraph endings:
Version A: "We can deliver the project by Friday, although resources are constrained this week."
Version B: "We can deliver the project by Friday. But resources are constrained this week, so the team will need to prioritise this above other tasks."
Version B splits the good news from the caveat. The reader registers both. Version A buries the caveat in a subordinate clause where it can be skimmed past. When the caveat matters, as it often does in business, version B does the job more honestly. Good opening sentences for global email operate on the same logic: front-load the point so the reader can't miss it.
When to use a different word instead
Frequency is the only real check. If three consecutive sentences begin with "but," the writing starts to feel breathless and unplanned. Vary the openings. Sometimes "however" fits because the sentence is long and formal. Sometimes restructuring removes the need for a connector at all.
Also watch for the difference between contrast and addition. "But" signals contrast. "And" signals addition. Using "but" when you mean "and" sends the wrong tonal signal. "The report is complete and the figures are attached" doesn't want a "but." Only use it when there's a real turn in the logic.
There are also specific register contexts where you'd avoid it. Formal legal documents and heavily structured academic writing tend to prefer "however" or restructured sentences. If you're unsure about your organisation's house style, check whether your existing documents use sentence-initial conjunctions. Most do.
A note on "and," "or," and "so" at the start
The same logic applies to the other coordinating conjunctions. "And" at the start of a sentence adds emphasis to an accumulation. "Or" opens a conditional branch. "So" introduces a consequence. All three appear at the start of sentences in published books, respected journalism, and top-tier business communication.
Getting comfortable with this frees up your writing considerably. Instead of reaching for "in addition," "alternatively," or "therefore" every time, you can use shorter words that do the same job faster. This matters especially in emails, where every extra word costs a fraction of a reader's attention. Even something as small as knowing "looking forward to" versus "I look forward to" signals that you understand how small word choices carry tonal weight.
The practical takeaway
Starting a sentence with "but" is grammatically fine. It's stylistically useful. Use it when you want to signal a clear contrast, when you want a short punchy sentence to land after a longer one, or when the alternatives ("however," "that said," "nevertheless") feel too heavy for the context.
The only thing to watch is overuse. Reach for it deliberately, not reflexively, and your writing will be cleaner for it. The writers who avoid it entirely aren't following a rule. They're following a myth.