Calculator
How to use this calculator
- Enter the amount due and any partial payment already made.
- Select the due date and the actual payment date.
- Add a grace period if your agreement allows it.
- Choose the fee model, then fill only its required fields.
- Optionally set minimums, maximums, caps, and fee taxes.
- Press Calculate to see totals, then download your summary.
Formula used
- flat: fee = flat_fee (if days_late > 0)
- percent once: fee = balance × (percent_fee/100)
- daily: fee = balance × (daily_percent/100) × days_late
- monthly: fee = balance × (monthly_percent/100) × (days_late/30)
- APR simple: fee = balance × (apr/100) × (days_late/365)
- APR daily: fee = balance × ((1+apr/100/365)^days_late − 1)
- tiered daily: fee = Σ balance × (tier_rate/100) × tier_days
- minimum: if 0 < fee < min_fee → fee = min_fee
- percent cap: fee ≤ balance × (cap_percent/100)
- maximum: fee ≤ max_fee (if max_fee > 0)
- tax: tax = fee × (tax_rate/100); total_fee = fee + tax
Example data table
| Amount Due | Due Date | Payment Date | Grace | Daily Rate | Late Days | Fee | Total Due |
|---|---|---|---|---|---|---|---|
| $1,200.00 | 2026-01-10 | 2026-02-01 | 5 | 0.1%/day | 17 | $20.40 | $1,220.40 |
Payment timing inputs and late-day logic
Late charges depend on dates and a clear grace period. The calculator converts the due date and payment date into days late, then subtracts grace days. For example, a bill due 2026-01-10 paid 2026-02-01 is 22 days apart; with five grace days, chargeable lateness becomes 17 days. This approach matches common billing systems that count calendar days, not business days.
Comparing policy models with numeric examples
Different agreements price lateness differently. A flat fee of 25 applies once when any chargeable day exists. A one-time 2.5% rule on a 1,200 balance produces 30. Daily pricing scales faster: 0.10% per day for 17 days yields 20.40, while a 3.0% monthly rate approximates 20.40 × (30/17) if the same balance stays unpaid. Penalty APR settings illustrate interest-style fees; at 18% APR, 17 days of simple interest adds about 10.06 on 1,200.
Managing caps, minimums, and regulatory limits
Controls prevent fees from becoming punitive. A minimum ensures small balances still generate an administrative charge, while a maximum limits exposure for long delays. A percentage cap, such as 10% of balance, keeps fees below 120 on a 1,200 balance. Tiered daily rates can escalate after day 30 significantly later. These guardrails help align outcomes with internal policy and consumer-facing disclosures.
Forecasting monthly cash impact from delinquencies
Finance teams can model expected fee income and customer burden. If 1,000 invoices average 800 and 6% become 15 days late at 0.08% daily, the expected fee base is 1,000 × 0.06 × 800 × 0.0008 × 15 = 576. Adding a 5% tax on the fee raises the total by 28.80, useful for budgeting and customer communications.
Building consistent records for disputes and audits
Operationally, consistency matters more than complexity. Store the input values, the chosen model, and the computed breakdown for each account. Exporting CSV supports reconciliation, while the PDF summary can accompany statements. Keeping a clear trail of dates, rates, and caps reduces dispute time and improves audit readiness.
FAQs
What are grace days and chargeable late days?
Grace days are fee-free days after the due date. Chargeable late days are the remaining late days after subtracting grace. If payment is early or within grace, the chargeable value becomes zero.
Which model fits credit-card style penalties?
Use Penalty APR when your terms quote an annual rate. Choose simple, daily, or monthly compounding to mirror your statement method. The calculator applies the rate only to the unpaid balance and only for chargeable late days.
How do minimum, maximum, and percentage caps interact?
The calculator applies a minimum first, then the percentage cap, then the maximum. This keeps tiny fees from disappearing while still limiting extreme outcomes. Disable any control by entering 0 for that field.
Why does the monthly rate use days divided by 30?
Many billing systems approximate a month as 30 days for penalty calculations. The calculator converts chargeable late days into a month fraction using days/30. For exact month boundaries, use a tiered approach or APR with monthly compounding.
Is tax applied to the full balance?
No. The tax rate is applied only to the computed late fee, not to the principal balance. Total due equals balance plus fee plus any fee tax.
What should I keep for dispute resolution?
Save the due date, payment date, grace days, model settings, and cap values used. The breakdown table plus CSV export shows the inputs and the computed fee. This makes it easier to explain outcomes and resolve complaints quickly.