Private Investigator Invoice Template
A private investigator's invoice has to justify every hour without exposing the case. Clients, and the attorneys who often engage investigators for them, check three things: that each block of time matches a date and a task in the engagement letter, that expenses are real and at the agreed rate, and that the retainer was applied correctly. This template is built around those checks. Time is listed by date and task (surveillance, interviews, records research, report writing) at the rate per investigator; mileage shows miles driven times the agreed rate per mile; database, court and records fees appear at cost with a reference; and the retainer received is subtracted from the total so the balance due, or the retainer left, is plain. Identify the matter by your case number and the client's reference, not by the subject's name or your findings: the report carries the findings, and the invoice may be seen by people who should not. Your state license number goes in the header. The download is an editable HTML invoice with invoice number, dates, a line-item table and totals; fill it in your browser and print it or save it as PDF.
Preview this editable document
Download the HTML file to edit its fields, then print or save as PDF. Totals are entered manually.
What This Template Includes
- Investigator or agency name and state license number
- Client, and the engaging attorney and matter reference if any
- Your case or file number (no subject details or findings)
- Engagement letter date and agreed rates
- Hours by date and task: surveillance, interviews, records research
- Rate per investigator, with any minimum or after-hours terms
- Mileage: miles driven × agreed rate per mile
- Database, records and court fees at cost, with reference
- Travel, lodging and other expenses, with receipts
- Report preparation and photo or video evidence handling
- Retainer received and amount applied to this invoice
- Retainer remaining or replenishment requested
How to Create Your Private Investigator Invoice
- 01
Describe your work
Type a plain English description of the services you provided, the client, and the amount.
- 02
AI generates your invoice
InvoiceQuickly's AI drafts the client, line items, dates, and totals for you to review before saving.
- 03
Review, download, and send
Check every detail, download the PDF, or use Pro to email the PDF directly to your client.
Recommended Payment Terms
If you take a retainer before starting and bill against it, write the method in the engagement letter and repeat it on every invoice: retainer received, amount applied, balance due or retainer left. Decide in advance whether a retainer is refundable if the case closes early, and whether the client must top it up when it falls below a set amount. Bill on a fixed cycle (weekly during active surveillance, or at each case milestone) so the client never meets a large surprise total; long gaps between invoices are what turn a reasonable case cost into a dispute. For attorney clients, ask whether the firm pays you directly or passes the invoice to its client, and who approves it. Mileage is billed at whatever rate your engagement letter sets; if you tie it to the IRS business standard mileage rate, remember that it is a tax-deduction figure, not a legal billing rate. Before charging interest on overdue balances, check your state's rules.
Need help writing payment terms? Read our guide to invoice payment terms for best practices and templates.
Tax Information
Sales tax on investigation services depends on the state. Texas is an example where it applies: its rule on security services (34 Tex. Admin. Code §3.333) covers services that need a license under Occupations Code §1702.101, which includes investigations companies, and says charges for security service to property or persons located in Texas are subject to sales tax. The taxable amount includes expenses directly related to and incurred while providing the service, even when they are billed separately. Texas's state rate is 6.25%, plus up to 2% local tax. Other states treat these services differently, so check your own state revenue department and apply the result the same way on every invoice. Business clients who pay you $2,000 or more in a tax year beginning after 2025 generally report it on Form 1099-NEC and will ask for a Form W-9 (IRS). InvoiceQuickly applies one tax percentage to the whole invoice after any discount, which suits a rule like Texas's, and copies your saved tax ID into new invoice PDFs; keep professional licence details in the notes. General information, not legal or tax advice.
Industry context (2026)
Private investigation is a small, licensed occupation. The US Bureau of Labor Statistics counts 39,500 private detective and investigator jobs in 2025, with a median wage of $24.62 an hour ($51,220 a year) for employees (the figure excludes the self-employed), notes that most states require investigators to be licensed, and describes schedules that include early mornings, nights and weekends for surveillance (Occupational Outlook Handbook, accessed 28 October 2026). Licensing is state by state: in California, for example, the Bureau of Security and Investigative Services licenses investigators, whom it describes as individuals who investigate crimes, identity, lost property, causes of losses and evidence for court. Tax treatment also varies: Texas taxes licensed investigation services as security services, including related expenses (34 Tex. Admin. Code §3.333). For mileage, the IRS business standard mileage rate for 2026 is 72.5 cents a mile from 1 January to 30 June and 76 cents from 1 July to 31 December (IRS, accessed 28 October 2026). General information, not legal or tax advice; last reviewed October 2026.
Worked example
Worked example (illustrative rates, not market data): a Texas investigations company is engaged by a law firm on 2 October 2026 for surveillance on matter reference 26-114, at $85 an hour per investigator, mileage at the IRS business rate in effect, and database fees at cost. The firm paid a $2,000 retainer on 2 October. Invoice PI-0318 is issued on 20 October, due in 15 days. Line 1: surveillance, one investigator, 14 October 06:00 to 14:00, 15 October 06:00 to 12:30 and 16 October 07:00 to 14:00, 21.5 hours × $85.00 = $1,827.50. Line 2: records and database research, 13 October, 2 hours × $85.00 = $170.00. Line 3: report preparation, 17 October, 3 hours × $85.00 = $255.00. Line 4: database search fees at cost, 4 searches, receipts attached, $48.00. Line 5: mileage, 212 miles × $0.76 (IRS rate from 1 July 2026) = $161.12. Subtotal $2,461.62. Sales tax at an assumed 8.25% combined Texas rate, applied to the whole amount including expenses: $203.08. Total $2,664.70. Less retainer applied (received 2 October): $2,000.00. Balance due $664.70; retainer remaining $0.00. Notes: 'Matter 26-114. Hours match the activity log in the report delivered 17 October. A new $2,000 retainer is required before further surveillance.' The tax line follows the Texas rule that related expenses are part of the taxable price; in a state that does not tax investigations, the tax line would be $0.00 and the balance $461.62.
Common mistakes to avoid
Findings on the invoice
An invoice that says what the subject did travels through accounts payable and may be produced in litigation. Describe tasks and times; keep findings in the report.
Hours that do not match the report
If the invoice says 21.5 hours and the activity log shows 19, the client will pay the lower figure. Build both from the same time log.
Mileage at the wrong rate
Using one rate for the whole of 2026 overstates or understates miles driven before 1 July if your letter ties mileage to the IRS rate. Bill each trip at the rate for its date.
Leaving expenses out of the tax base
In Texas, related expenses are part of the taxable price of security services even when itemized. Taxing only the hours under-collects.
No retainer arithmetic
'Balance due: $664.70' with no retainer line invites a call. Show received, applied and remaining on every invoice.
Invoicing Tips
- 1Describe tasks, not findings: 'Surveillance, 14 Oct, 06:00 to 14:00' rather than what you saw. The report is the place for evidence.
- 2Log hours in the same blocks your report uses, so the client can lay the invoice next to the activity log and see they match.
- 3Show mileage as miles × rate with the rate's basis ('212 miles × $0.76, per engagement letter'). If you tie mileage to the IRS rate, check which rate applied on the dates you drove: the 2026 rate changed on 1 July.
- 4Attach receipts or a fee list for database searches, court copies and records requests, and bill them at cost unless your engagement letter states a mark-up.
- 5Print the retainer arithmetic on every invoice: received, applied to date, remaining. It answers the question clients ask most.
- 6Put your license number in the header. It is the first thing a new client or an attorney checks.
Related Resources
Frequently Asked Questions
What should a private investigator invoice include?
Your agency name and state license number, the client and any engaging attorney, your case number, an invoice number and dates, hours by date and task at the agreed rate, mileage and expenses at the agreed rates with receipts, report preparation, any tax, the retainer applied, the balance due and how to pay. Leave findings and the subject's personal details off.
How do private investigators bill: hourly or flat fee?
Either, as long as it matches the engagement letter. Surveillance and field work suit hourly billing per investigator, plus mileage and expenses, because the time a case takes is hard to predict. Defined tasks such as a records search or a single background report suit a flat fee. The invoice should mirror the letter line for line.
How do I show a retainer on an investigator invoice?
List the work and expenses as normal, total them, then subtract the retainer applied with the date it was received. Show what is left of the retainer, or the balance due if the work exceeded it, and any top-up your engagement letter requires.
What mileage rate can a private investigator charge?
The rate in your engagement letter. If the letter ties it to the IRS business standard mileage rate, that rate was 72.5 cents a mile for January to June 2026 and 76 cents from 1 July 2026. The IRS rate sets what can be deducted, not what you may bill.
Do private investigators charge sales tax?
In some states. Texas treats investigation services that need a license under its Private Security Act as taxable security services, including related expenses. Other states treat them differently, so check your state revenue department.
Should the investigator's license number be on the invoice?
Put it there. Licensing is set by each state, and clients and attorneys use the number to confirm you are licensed where the work was done. Check your licensing agency's rules on where else it must appear, such as advertising.
Can I create a private investigator invoice in InvoiceQuickly?
Yes. Type or say what you did, for example '21.5 hours surveillance at $85, 212 miles at 76 cents, $48 database fees', and InvoiceQuickly drafts an editable invoice you review before saving. Record the retainer as a payment on the invoice so the remaining balance updates. It does not manage cases or track retainer balances across invoices.