Math Errors on Your Bill

Simple Errors, Big Impact

Math errors on medical bills are more common than you'd expect. A simple calculation mistake can mean paying more than you owe.

Types of Math Errors

Addition Errors

• Line items don't add up to subtotal
• Subtotals don't add up to total
• Multiple pages with incorrect running totals

Percentage Errors

• Coinsurance calculated incorrectly
• Discount percentages applied wrong
• Tax calculations on medical services (often shouldn't exist)

Credit Application Errors

• Payments not properly credited
• Insurance payment not reflected
• Adjustments not subtracted

Rounding Issues

• Excessive rounding up
• Inconsistent rounding across line items
• Rounding that always favors the provider

How to Check the Math

Step 1: Add Up Line Items

Use a calculator to add all individual charges:

• Write down each line item amount
• Sum them manually
• Compare to stated subtotal

Step 2: Verify Adjustments

Check that discounts are applied correctly:

• Calculate percentages yourself
• Verify contractual adjustments match EOB
• Ensure credits are subtracted, not added

Step 3: Confirm Final Total

Verify the final amount:

  Total Charges
- Adjustments
- Insurance Payment
- Prior Payments
= Amount Due

Step 4: Cross-Reference with EOB

Your EOB should match:

• Allowed amounts
• Insurance payments
• Your responsibility

Common Calculation Mistakes

Coinsurance Calculation

Incorrect:

• Billed: $1,000
• Your 20%: $200 (of billed amount)

Correct:

• Billed: $1,000
• Allowed: $800
• Your 20%: $160 (of allowed amount)

Payment Application

Incorrect:

• Total: $500
• Insurance paid: $400
• Previous payment: $50
• Due: $100 (should be $50)

Adjustment Math

Incorrect:

• Charges: $1,000
• Adjustment: $200
• Subtotal: $900 (should be $800)

Red Flags to Watch

Totals That Don't Add Up

• Sum of items doesn't match subtotal
• Stated total differs from your calculation

Percentages That Seem High

• Cost-sharing higher than policy states
• Discounts smaller than expected

Confusing Credits

• Credits shown as positive numbers
• Payments not reducing balance

Missing Information

• Calculations not shown
• Can't verify how total was reached

How to Dispute Math Errors

Step 1: Document the Error

• Show your calculation
• Highlight the discrepancy
• Note the amount of overcharge

Step 2: Contact Billing

• Point out the specific error
• Provide your calculation
• Request corrected bill

Step 3: Follow Up

• Get confirmation of correction
• Request updated statement
• Verify the math is now correct

Example Dispute

"I am writing to dispute the calculation on my bill dated [date]. The line items total $[your calculation], but the bill shows a subtotal of $[their amount]. This is a discrepancy of $[difference]. Please review the arithmetic and provide a corrected statement."

Prevention Tips

• Always request itemized bills
• Check math as soon as bill arrives
• Keep records of all payments made
• Compare every bill to EOB

Math errors are easy to spot if you take the time to verify calculations. Don't assume the billing department got it right.