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//// Business · Freelance Billing

Late Fee Notice Calculator

Invoice amount, days overdue, monthly rate. Get the late fee, daily accrual, simple-vs-compound comparison, and a ready-to-send past-due email notice that adapts to how overdue the invoice is.

Where this fits

📦 Business & Seller OpsGoing 1099FreelancersFounders

This tool lives inside Going 1099 and is most useful for freelancers and founders.

Corp Tax Rate21%
SE Threshold$400
FICA Cap 2024$168,600

Invoice Details

Plain English

This invoice is 45 days overdue. The client now owes $4,585.50 — that's $85.50 in late fees on top of the original $4,500.00.

Late fee
$85.50
38 effective days
Total now owed
$4,585.50
$4,500.00 + fees
Daily accrual
$2.25
Adds per day while overdue
If compounded
$4,585.67
+$0.17 vs simple

Past-Due Notice — Email Template

Subject: PAST DUE — Invoice (38 days overdue)

Hi there,

Invoice for $4,500.00 is now 45 days past due. Per our agreement, a late fee of 1.5% per month applies after the 7-day grace period.

Current balance:
  • Original invoice: $4,500.00
  • Late fees accrued (38 days): $85.50
  • Total now owed: $4,585.50

Daily accrual moving forward: $2.25/day

Please remit payment within the next 7 business days to avoid further fees. If there's an issue I should know about, reply to this email and let's sort it out.

Thanks,

Simple vs Compound Interest

Method

Fee

Total

Simple (standard)

$85.50

$4,585.50

Compound (monthly)

$85.67

$4,585.67

Compound premium

—

+$0.17

1

Effective days in fee

effectiveDays = max(0, daysOverdue − gracePeriod)

= max(0, 45 − 7)

= 38 days

Grace period comes off the top — no fees accrue during it

2

Daily accrual rate

dailyAccrual = invoice × (monthlyRate / 30)

= $4,500.00 × (1.5% / 30)

= $2.25/day

3

Simple interest fee

simpleFee = invoice × monthlyRate × (days / 30)

= $4,500.00 × 0.015 × 1.267

= $85.50

Linear — fee accrues on the original balance only

4

Compound interest fee

compoundFee = invoice × ((1 + monthlyRate)^months − 1)

= $4,500.00 × ((1 + 0.015)^1.267 − 1)

= $85.67

Compound premium vs simple: $0.17 extra

5

Total owed

total = invoice + lateFee

= Simple: $4,585.50 · Compound: $4,585.67

Most contracts specify simple interest at 1.5%/mo = 18% APR — the cap in most US states for unsecured debt

Key insight

Most freelance contracts use 1.5%/month simple interest (18% APR). Some states cap the enforceable rate lower — check your state's usury statute before charging more.

Use this result in →

💸Invoice Late Fee (full)📅Invoice Due Date📊Invoice Aging Report

#ShowYourWork

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