1. SUBJECT LINE: "Invoice #1042 - now 6 days past due" / "Quick reminder: Invoice #1042 ($3,200)" 2. EMAIL BODY: Hi there, just a quick note that Invoice #1042 for $3,200, due June 15, is now 6 days past due. You've been a reliable client for over a year with no late payments before this, so this is likely just a scheduling gap on your end. Could you confirm when we can expect payment, or let us know if there's an issue with the invoice itself? If we don't hear back or receive payment, we'll follow up again in a week. Thanks for taking care of this. 3. TONE ESCALATION LEVEL: Friendly first nudge - short overdue period and strong payment history support a light, assumption-of-good-faith tone. 4. INTERNAL NOTE: No action needed yet - if unpaid after the second reminder next week, escalate to a firmer notice given the account's otherwise clean history.