Arrears Balance Calculator: Amounts Due and Paid
Reconcile the confirmed amount owed against payments already received.
Work & pay
Gross Back Pay and Wage Arrears Calculator
Multiply the pay shortfall per unit by the affected units and add any confirmed adjustment. Calculate periods with different rates separately; the result is gross arrears, not the net payslip amount.
Your numbers
How the calculation works
Gross back pay reconciles a confirmed pay rate with the rate actually paid over a matching quantity of hours, days or pay periods. A separate adjustment allows another established gross difference to be included without changing the rate comparison.
Back pay = (correct pay per unit − paid pay per unit) × affected units + confirmed adjustment.
Find the shortfall per unit
Subtract gross pay actually paid from the correct gross pay. This preserves a negative difference if the entered paid rate was higher.
Apply it to the affected quantity
Multiply the per-unit difference by the number of matching units. The calculation assumes that difference applies consistently across every included unit.
Add the separate adjustment
Apply the confirmed adjustment once to obtain total gross back pay. The result is not rounded into a payroll tax calculation or converted to take-home money.
Worked example: Hourly shortfall
Sample inputs demonstrate the method. They are not a forecast or product offer.
The first example should pay €20 per hour but paid €18 for 80 hours. The shortfall is €2 per hour; multiplying by 80 gives €160 gross back pay. The separate adjustment is zero, so it does not change that result.
- Correct gross pay per unit (€)
- 20
- Gross pay actually paid per unit (€)
- 18
- Affected units
- 80
- Other confirmed gross adjustment (€)
- 0
Expected result
- Gross back pay
- €160.00
Worked example: Monthly adjustment
Sample inputs demonstrate the method. They are not a forecast or product offer.
- Correct gross pay per unit (€)
- 3000
- Gross pay actually paid per unit (€)
- 2800
- Affected units
- 3
- Other confirmed gross adjustment (€)
- 100
Expected result
- Gross back pay
- €700.00
Understanding your result
A positive result describes a gross shortfall under the supplied figures. A negative result describes the opposite numerical position, without deciding whether repayment can lawfully be required.
Use payroll records to confirm rates, units and adjustments. This arithmetic does not establish eligibility, a legal award, interest on arrears or the deductions applied when the amount is processed.
Questions you might have
What does this back pay calculator include?
Estimate a gross pay shortfall from the correct pay per unit, the amount paid and the number of affected units.
Which assumptions should I check?
This estimates gross arrears, not net payment or a legal award. Separate periods with different pay rates must be calculated separately. Payroll tax depends on actual processing rules.
Choosing the right inputs
- Correct gross pay per unit
- Enter the correct gross amount per chosen unit. The paid amount must use exactly the same unit, currency and pay basis.
- Affected units
- Use the number of affected hours, days or periods. If the applicable rates changed, split the history into separate calculations with consistent rates.
- Other confirmed gross adjustment
- Include only an additional confirmed gross adjustment not already captured by the per-unit difference. A negative adjustment reduces the calculated total.
Common mistakes to avoid
- Do not multiply a monthly pay difference by affected hours.
- An adjustment already included in the correct or paid rate must not be added again as a separate amount.
Assumptions to check
- This estimates gross arrears, not net payment or a legal award. Separate periods with different pay rates must be calculated separately. Payroll tax depends on actual processing rules.
Sources and method
Read our calculation and testing approach.