Accountants Invoice Total (Hourly) Formula
Learn how an hourly accountant invoice total is calculated from time fees, reimbursable expenses and tax.
An hourly accounting invoice starts with the charge for billable time, adds eligible expenses, and then applies the selected tax rate. This calculation helps estimate the amount due before an invoice is issued.
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Total Invoice Amount
Where:
Multiply the hourly rate by the billable hours, add reimbursable expenses, then add tax calculated on that pre-tax subtotal.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| hourlyRate - Hourly rate | The agreed fee charged for each billable hour of accounting work. | currency |
| billableHours - Billable hours | The total time charged to the client, including fractional hours where applicable. | hours |
| expenses - Reimbursable expenses | Approved out-of-pocket costs added to the invoice. | currency |
| taxRate - Tax rate | The sales tax, VAT, GST or other tax percentage applied to the invoice subtotal. | percent |
Step-by-Step Calculation
Calculate the hourly work charge
Multiply the agreed hourly rate by the total billable hours.
labourCharge = hourlyRate * billableHours
Add reimbursable expenses
Add chargeable expenses to the hourly work charge to find the pre-tax invoice subtotal.
subtotal = labourCharge + expenses
Convert the tax percentage
Divide the entered tax percentage by 100 before using it in the tax calculation.
taxDecimal = taxRate / 100
Calculate tax
Apply the tax rate to the pre-tax subtotal. This calculator applies tax to both time fees and expenses.
taxAmount = subtotal * taxDecimal
Calculate the total due
Add the tax amount to the pre-tax subtotal to estimate the final invoice amount.
invoiceTotal = subtotal + taxAmount
Example: 8 hours of accounting work with expenses
Calculate work charge
$150.00 × 8
$1,200.00
Calculate pre-tax subtotal
$1,200.00 + $50.00
$1,250.00
Calculate tax
$1,250.00 × (20 ÷ 100)
$250.00
Calculate invoice total
$1,250.00 + $250.00
$1,500.00
Final Result
Estimated total invoice amount: $1,500.00.
Assumptions
- ✓All billable time is charged at one hourly rate.
- ✓The entered expenses are reimbursable and are billed at the amounts entered.
- ✓The selected tax rate applies to the whole pre-tax subtotal, including expenses.
- ✓No discount, retainer credit, write-off, deposit, late fee or prior payment is included.
Limitations
- !Tax treatment of expenses and professional services can vary by jurisdiction and invoice arrangement.
- !The calculation does not determine whether tax registration, tax charging or a particular rate applies.
- !It does not account for multiple hourly rates, fixed-fee work, capped fees or tiered pricing.
- !Rounding practices on actual invoices may create a small difference from the displayed estimate.
Common Mistakes to Avoid
Entering minutes as a decimal incorrectly; 30 minutes is 0.5 hours, not 0.30 hours.
Applying the tax rate directly as a whole number instead of dividing it by 100 in a manual calculation.
Leaving reimbursable expenses out of the pre-tax subtotal when they are intended to be invoiced.
Adding tax twice by entering tax-inclusive expenses without adjusting them first.
Treating a retainer payment or discount as an expense rather than applying it separately.
Related Formulas
Frequently Asked Questions
What is the formula for an hourly accountant invoice?
The formula is: (hourly rate × billable hours + reimbursable expenses) × (1 + tax rate ÷ 100).
How is the hourly work charge calculated?
Multiply the hourly rate by the total billable hours. For example, 6.5 hours at $120 per hour produces a work charge of $780.
How do I calculate tax on an accountant invoice?
Multiply the pre-tax subtotal by the tax rate divided by 100. The pre-tax subtotal is the time charge plus the entered expenses.
Are expenses included before tax?
In this calculator, yes. Expenses are added to the work charge before tax is calculated. Actual tax treatment may differ by jurisdiction or expense type.
Can billable hours include fractions?
Yes. Use decimal hours, such as 0.25 for 15 minutes, 0.5 for 30 minutes, and 1.75 for one hour and 45 minutes.
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