Quick question on last week’s invoice #1234
Type: Finance / Billing
Tone: Direct, courteous
This subject line links the email to a specific document, such as invoice #1234, so the accounts payable department can quickly process it.
Use it when you spot a mismatch, such as a missing PO number, and require a quick response to maintain smooth cash flow.
Billing Error Alert, Our Sorry and Refund Plan
Type: Billing
Tone: corrective, reassuring
Here’s a simple formula for apology email subject lines: Admit your mistake and apologize for it.
Spell out the mistake and offer a solution. Avoid jargon—technical explanations can undermine trust.
Payment due today for invoice #[invoice number]
Type
Financial, Billing, B2B
Tone
Clear and concise
Why this line works
Numbers leap off cluttered inboxes, and adding the invoice ID provides instant context. Avoid jargon, keep verbs quick, “due today”, and reference the invoice only once to limit cognitive load.
Hidden pitfalls to avoid
- Skip vague wording like “outstanding balance.” Specificity feels transparent.
- Include the payment link inside the email so recipients need one click, not three.
Example email
Hello [First Name],
I’m sending this gentle reminder that invoice #[invoice number] reaches its due date today.
If you already handled it, please disregard. Otherwise, you can settle securely through the button below.
Thanks for keeping our books tidy.
Best,
Sam
