Private Investigator Invoice Template (Free + Example)

Private investigator invoice template: bill hourly surveillance, mileage, database searches and reports, apply the retainer, and keep case details confidential.

By Invoice Creator Editorial Team 9 min readPublished: October 29, 2026

Quick answer: A private investigator invoice template bills a client for investigative work: hourly surveillance and research, travel time, mileage, database or records fees, report writing and court time. It shows the case number, dates and hours, applies any retainer, and states the balance due without revealing confidential case findings.

Private investigation is an hourly business with a lot of small costs: miles driven, records ordered, video storage, sometimes a second operative. Clients range from worried individuals to insurance carriers and law firms, and each wants a different level of detail. This guide shows how to structure a PI invoice, how to bill against a retainer, and includes a worked example with real numbers.

What is a private investigator invoice?

A private investigator invoice is the bill a licensed investigator or agency sends after (or during) a case. It lists billable time, expenses and fees, subtracts any retainer, and asks for payment by a set date. It is different from your investigative report: the report contains findings, the invoice contains only what is needed to justify the charges.

Typical PI clients include:

Attorneys and law firms needing witness locates, background research and trial support.
Insurance carriers and TPAs ordering claims and surveillance investigations.
Employers requesting workplace or pre-employment investigations (subject to background check laws).
Individuals with family, infidelity, asset or missing person matters.

The structure is close to a legal invoice: time entries by date and task, then expenses. Agencies that also provide guards or patrol should keep those on a separate security services invoice.

What to include on a PI invoice

Field	Example	Notes
Agency name and license number	Northline Investigations, License #A-12345	Check your state board's rules on displaying it
Client and reference	Harper and Cole LLP, matter 24-0391	Use the client's matter or claim number
Case or file number	NI-2026-118	Your internal reference
Invoice number and dates	INV-1187, issued and due dates	Sequential and unique
Time entries	Date, activity, investigator, hours, rate	Generic activity labels, no findings
Mileage	Miles x rate	Rate per your agreement
Expenses	Database searches, court records, parking, tolls	At cost or with stated markup
Retainer applied	Retainer received and amount applied	Show the remaining balance
Terms	Due date, late fee, payment methods	Match the engagement agreement

How private investigators charge: hourly, flat fee and retainer

Hourly rates

Most investigative work is hourly, and rates vary by state, specialty and whether the client is an individual, attorney or insurer. Published surveys differ, so set your rate from your own costs and local competition. Common hourly categories include surveillance, field interviews, research, report writing, and court testimony (often billed at a higher rate with a minimum, such as half a day).

Minimums and blocks

Surveillance is often sold with a daily minimum, such as 4 or 8 hours, because an investigator who sets up for a subject cannot take other work that day. Spell out the minimum in the agreement and on the invoice line.

Flat fees

Packaged services such as a basic background check, an asset search or a skip trace are often flat-fee. List them as a single line with a clear description.

Retainers

Most agencies take a retainer before starting, especially from individuals. Each invoice then shows the work done and draws the balance down. Our retainer invoice guide explains the mechanics and wording.

Billing mileage and expenses

Mileage is often the largest expense line for field work. Many agencies use the IRS standard business mileage rate as their reimbursement rate. For 2026 the IRS set it at 72.5 cents per mile from January 1, and trade publications reported a mid-year increase for miles driven from July 1; confirm the current figure on the IRS standard mileage rates page before quoting it. You can also agree your own rate in the contract. Our mileage invoice guide shows how to lay out trip lines, and the mileage log template keeps the records that back them up.

Other common PI expenses:

Database and public records search fees
Court record copies and certified documents
Parking, tolls and public transport
Video storage, transcription and media copies
Second investigator for two-car surveillance
Out-of-area lodging and meals, if agreed

Say in your agreement whether expenses are billed at cost or with a handling markup, then bill consistently. For a general approach to pass-through costs, see how to bill reimbursable expenses.

Example private investigator invoice

This example bills an attorney for a witness locate and two days of surveillance. Rates are illustrative, not a market survey.

Date	Description	Qty	Rate	Amount
Oct 20	Records and database research, witness locate	2.5 hr	$85.00	$212.50
Oct 22	Surveillance (8-hour minimum)	8.0 hr	$95.00	$760.00
Oct 23	Surveillance	9.5 hr	$95.00	$902.50
Oct 24	Field interview and travel	3.0 hr	$85.00	$255.00
Oct 26	Report preparation and video review	2.0 hr	$85.00	$170.00
Oct 20-24	Mileage	186 mi	$0.725	$134.85
Oct 20	Database search fees (at cost)	1	$48.00	$48.00
Oct 24	Parking and tolls (at cost)	1	$22.75	$22.75
Total charges				$2,505.60
Less retainer applied (received Oct 15)				-$2,000.00
Balance due				$505.60

The math: hours total 25.0 (2.5 + 8 + 9.5 + 3 + 2), 17.5 of them surveillance at $95 and 7.5 other work at $85, for $2,300.00 of labor. Add $134.85 mileage (186 x $0.725) and $70.75 of expenses to reach $2,505.60, then subtract the $2,000 retainer. The descriptions identify the activity but say nothing about the subject or what was observed.

How to create a PI invoice step by step

Log time daily. Record date, start and end time, activity and investigator. A timesheet template works if you have no case software.
Log miles and keep receipts. Odometer readings or GPS logs support mileage lines.
Open a new invoice in the free invoice generator with your agency details and license number.
Add the client's reference. Matter, claim or PO number goes near the top.
Enter time lines, then expenses. Keep labels generic and consistent.
Apply the retainer. Show the amount applied and the balance, or the remaining credit.
Set terms and send. Email the PDF invoice separately from the confidential report if the client prefers.

Confidentiality on PI invoices

Invoices travel through more hands than reports: bookkeepers, law firm billing staff, insurers' payables teams and sometimes the opposing side in a fee dispute. Keep the invoice factual and dull. Use the case number instead of the subject's name, describe activities generically, and never include photos, addresses of subjects or conclusions. Deliver findings only in the report, through whatever secure channel you agreed.

Billing different PI clients: individuals, attorneys and insurers

The same hour of surveillance can need three different invoice formats depending on who pays.

Client type	Typical terms	Invoice needs
Private individual	Retainer before work, top-ups as needed	Simple time and expense summary, retainer balance, plain-language descriptions
Law firm	Net 30, sometimes paid when the case resolves if agreed	Matter number, task-by-date entries, expenses at cost, sometimes billing codes
Insurance carrier or TPA	Rates and caps set by the carrier's guidelines	Claim number, adjuster name, hour caps per assignment, mileage per their policy
Employer or HR	Net 30, PO required	PO, department, neutral activity labels for workplace investigations

Insurance carriers in particular often publish vendor billing guidelines that cap surveillance hours per day, set mileage rates and refuse certain expenses. Read them before the assignment, because invoices that break the guidelines are cut automatically. For employer work involving background screening, federal and state consumer reporting laws may apply; confirm your obligations before you take the assignment.

Retainer accounting: keeping client funds straight

When you hold a retainer, you are holding the client's money until you earn it. Good practice is to:

Record the retainer as a liability (unearned revenue) when received, not as income.
Move amounts to income only as you invoice hours and expenses against it.
Send a statement with each invoice showing opening retainer, amounts applied and closing balance.
Refund any unused balance at the end of the case if the agreement says it is refundable, with a final zero-balance invoice.
Request a replenishment before the balance runs out, not after you have worked for free for a week.

Some states have specific rules for how licensed investigators handle client funds, so check with your licensing board. Clear retainer statements are also your best defense if a client later disputes the bill.

Common mistakes on private investigator invoices

Revealing findings in line items. "Subject seen at bar" belongs in the report, not the invoice.
Not showing the retainer. Clients need to see how their advance was used.
Billing minimums the agreement did not mention. A surprise 8-hour minimum causes disputes.
Lumping expenses. "Expenses: $300" invites questions; itemize.
Waiting until the case ends. On long cases, bill weekly or when the retainer runs low.
Ignoring sales tax rules. A few states tax investigative services; check your state.

This article is general information, not legal or tax advice. PI licensing and billing rules are set by each state.

PI invoice checklist before you send

Agency name, address and license number match your state registration.
Client reference (matter, claim or PO number) is at the top.
Every time entry has a date, activity label, hours and rate.
Surveillance minimums are applied only where the agreement allows them.
Mileage lines show miles and the agreed rate, with a log to back them up.
Expenses are itemized and receipts are attached or available.
Retainer received, amount applied and balance remaining are shown.
No subject names, addresses, photos or findings appear anywhere.
Due date is a calendar date, and payment methods are listed.

Running through this list takes two minutes and avoids most of the questions attorneys' billing departments and insurance adjusters send back.

Get paid for your investigation work

If you are chasing late payments from individual clients, our guides to late payment fees and payment terms help you set rules that hold up. A private investigator invoice template with clear time entries, itemized mileage and a visible retainer balance makes your bill easy to approve. Build one now with our free invoice generator: there is no sign-up, the PDF is created in your browser, and you can download it and send it straight to your client.

Frequently asked questions

How do private investigators usually bill clients?

Most bill by the hour for investigative work, with mileage and direct expenses added on top. Clients normally pay a retainer before work starts, and the investigator invoices against it, showing hours, expenses and the remaining balance. Some services, such as a background check or a process service attempt, are sold at a flat fee. Surveillance is often sold in blocks with a minimum number of hours per day.

What is a retainer for a private investigator?

A retainer is an advance payment the client makes before the case begins. The investigator draws against it as hours and expenses are incurred, and sends invoices or statements showing what was used. If the case uses less than the retainer, the agreement should say whether the unused amount is refunded. If it runs over, the client pays an additional invoice or tops up the retainer.

Should a PI invoice include case details?

Include enough to identify the work, such as a case or file number, the date range and the type of activity, but leave sensitive details in the written report. Invoices pass through accounting staff, law firm billing systems and email, so avoid naming the subject or describing findings on the invoice. A line such as surveillance, case 2026-118, 9.5 hours is usually enough.

Can a private investigator charge for travel time?

Many do, often at the same or a reduced hourly rate, and the policy should be in the engagement agreement. Travel time is commonly billed portal to portal, from the office to the assignment and back, plus mileage per mile. Some agencies waive travel inside a local radius. Whatever the policy, show travel hours and mileage on separate invoice lines so the client can see what they paid for.

Do I need to put my license number on a PI invoice?

Many states require licensed private investigators or agencies to show their license number on contracts, advertising or business documents, and some boards expect it on invoices and reports too. Requirements differ by state, so check your state licensing board. Even where it is not required, including the license number builds trust and helps attorneys and insurers verify you quickly.

How do attorneys pay private investigators?

When an attorney hires you, the law firm is usually your client and pays your invoice, then bills the cost to its own client as a case expense. Attorneys often want hours broken out by task and date, and some need invoices formatted to match their billing system. Ask about the firm's requirements at intake, and reference the matter number the firm gives you.

Are private investigation services subject to sales tax?

It depends on the state. Most states do not tax investigative services, but some states with broad sales taxes on services do include detective or security services in the taxable list. Check your state's department of revenue guidance, and if your service is taxable, show the tax as its own line on the invoice rather than folding it into the hourly rate.

What payment terms should a PI agency use?

Retainer upfront is standard for individual clients, who may otherwise struggle to pay once they have the report. Law firms and insurers often get net 30 terms because they are repeat clients with established payment processes. Whatever terms you choose, state them in the agreement and on every invoice, and consider holding the final report until the balance is paid for non-retainer clients.

Invoice Creator Editorial Team

Guides on invoicing, cash flow and small-business finance from Invoice Creator, operated by Next Software Development Company. Content is reviewed for accuracy against the fields our own invoice generator produces.

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