Invoice Due Date Calculator

Due date calculation

due_date = invoice_date + net_days

Sun, April 12, 2026 + 30 days

= Tue, May 12, 2026

Net 30 terms: payment expected within 30 calendar days of invoice. Industry median DSO (Days Sales Outstanding) is ~30 days for U.S. small businesses.

PYMNTS / QuickBooks 2024 — U.S. small business DSO benchmarks

Days until due (from today)

days_remaining = due_date − today

Tue, May 12, 2026 − Apr 12, 2026

= 30 days remaining

Comfortable window — follow-up date is set 3 days before due.

Follow-up reminder date

follow_up = due_date − 3 days

Tue, May 12, 2026 − 3 days

= Sat, May 9, 2026

3-day advance reminder reduces late payments by 30–40% (Fundbox 2023 study). Add to your calendar via the .ics download.

Late fee if 30 days overdue (standard 1.5%/mo on $5k invoice)

late_fee = principal × 1.5% × months_overdue

$5,000 × 1.5% × 1 month

= $75.00/month · $2.50/day

1.5%/month = 18% APR — legally enforceable if stated in your contract. Always include late fee terms in writing before the project starts.

Standard commercial late fee: 1.5%/mo (18% APR) — enforceable in all 50 states with contract disclosure

Float cost — opportunity cost of outstanding receivable (30-day term)

float_cost = invoice_amount × 5% APY ÷ 365 × net_days

$5,000 × 5% ÷ 365 × 30

= $20.55 on $5k invoice

Every dollar you're owed costs you ~$0.6849/day in lost investment return. Net 15 vs Net 30 saves $10.27 on a $5k invoice — a strong argument for shorter terms.