Legal Billing Guide: How Lawyers Should Invoice for Billable Hours, Retainers, and Trust Accounting

Legal billing is unlike any other profession's invoicing. You are not just sending a bill for services rendered — you are navigating ethical obligations around trust accounts, billing formats dictated by corporate clients, fee arrangements that range from hourly to contingency to flat-rate hybrids, and bar association rules that vary by jurisdiction. Get it wrong and you do not just delay payment — you risk malpractice complaints and disciplinary action.

This guide covers the specific invoicing practices lawyers and law firms need, with practical advice you can apply whether you are a solo practitioner or managing a mid-size firm. For foundational invoice concepts, see our guide on how to create a professional invoice.

Billable Hours: The Foundation of Legal Invoicing

Most law firms still bill by the hour, and how you present those hours on an invoice directly affects whether the client pays without pushback.

What a billable hour entry should include

Every time entry on your invoice needs four elements:

• Date: The exact date the work was performed, not the date you got around to recording it.
• Timekeeper: The attorney or paralegal who performed the work, along with their billing rate.
• Description: A clear, specific narrative of what was done. "Legal research" tells the client nothing. "Researched case law on enforceability of non-compete agreements in Texas, reviewed Henderson v. Global Corp (2024) and three related decisions" tells the client exactly what they are paying for.
• Time: The duration in hours, typically in six-minute (0.1 hour) or fifteen-minute (0.25 hour) increments depending on your firm's billing convention.

The description problem

Vague time entries are the number one reason clients dispute legal invoices. Insurance companies, corporate legal departments, and sophisticated individual clients all scrutinize descriptions. Here are examples of bad versus good entries:

Bad: "Work on contract" — 2.5 hours at $350/hour = $875

Good: "Drafted sections 4-7 of asset purchase agreement including representations and warranties, indemnification provisions, and closing conditions; conferred with opposing counsel regarding proposed escrow terms" — 2.5 hours at $350/hour = $875

The good version justifies the time spent. The bad version invites the client to wonder what you actually did for two and a half hours.

Billing multiple timekeepers

When several attorneys and paralegals work on the same matter, list each person's entries separately with their individual rates. Group entries by date, then by timekeeper. Include a summary at the top showing each timekeeper's name, title, rate, and total hours on this invoice.

A typical summary looks like this:

Timekeeper	Role	Rate	Hours	Amount
J. Martinez	Partner	$450/hr	8.3	$3,735.00
S. Chen	Associate	$275/hr	22.7	$6,242.50
R. Okafor	Paralegal	$150/hr	14.1	$2,115.00
Total			45.1	$12,092.50

This gives the client a quick overview before they dig into the detailed entries below.

Retainer Billing and Trust Accounting

Retainer arrangements are standard in legal practice, and they come with strict ethical rules about how money is held and billed against.

Evergreen retainers vs earned retainers

There are two fundamentally different types, and mixing them up creates ethical problems:

• Evergreen (replenishing) retainer: The client deposits funds into your trust account. You bill against those funds monthly or as work is performed. When the balance drops below a threshold, the client replenishes. The money belongs to the client until you earn it.
• Earned-on-receipt retainer: A flat fee paid upfront that becomes your property immediately upon receipt. This is less common and only permissible in certain jurisdictions and arrangements.

For evergreen retainers, every invoice must show:

1. The trust account opening balance for the billing period
2. Each time entry and expense billed against the trust
3. The amount being drawn from the trust this period
4. The remaining trust balance after the draw
5. Whether a replenishment is needed

Trust accounting rules

Bar associations in every state require lawyers to maintain client trust funds in a separate IOLTA (Interest on Lawyers' Trust Accounts) account. Commingling client funds with your operating account is one of the most common grounds for disciplinary action.

Your invoice should clearly distinguish between:

• Fees earned: The amount being transferred from trust to your operating account based on work performed
• Expenses advanced: Costs you incurred on the client's behalf (filing fees, expert witness deposits, deposition transcripts) that are reimbursed from trust
• Trust balance: What remains in trust after this invoice's charges

Never draw from the trust account before sending the invoice and giving the client a reasonable opportunity to review it, unless your engagement letter specifically permits immediate draws. The safest practice is to send the invoice, wait for any objections, and then process the trust draw.

LEDES Format: When Corporate Clients Dictate Billing

If you do any work for insurance companies, large corporations, or government entities, you will encounter LEDES (Legal Electronic Data Exchange Standard) billing requirements. LEDES is a standardized electronic billing format that lets clients run your invoices through automated review software.

What LEDES requires

LEDES invoices use specific activity codes, expense codes, and task codes that categorize every entry. The most common standard is LEDES 1998B, which uses the Uniform Task-Based Management System (UTBMS) codes:

• Task codes (e.g., L110 for "Fact Investigation/Development," L310 for "Document Production")
• Activity codes (e.g., A101 for "Plan and prepare for," A104 for "Draft/revise")
• Expense codes (e.g., E101 for "Copying/reproduction," E107 for "Court fees")

Why LEDES matters for your cash flow

Corporate clients that require LEDES billing typically run your invoices through e-billing platforms like Legal Tracker, CounselLink, or Brightflag. These platforms automatically flag entries that violate the client's billing guidelines — vague descriptions, block billing (lumping multiple tasks into one time entry), excessive time on routine tasks, or work performed by attorneys above the approved staffing level.

Rejected entries mean delayed payment. Some corporate clients report rejection rates of 15-20% on first-submission invoices from firms that do not take LEDES compliance seriously.

If you regularly handle corporate or insurance defense work, using invoice software for lawyers that supports task code assignment and structured exports will save you hours of manual formatting every billing cycle.

Contingency Fee Billing

Contingency fee arrangements — where your fee is a percentage of the recovery — seem like they would simplify invoicing. No hourly billing means no time entries, right? Not quite.

What you still need to invoice

Even on contingency, you need clear documentation of:

• Expenses: Most contingency agreements require the client to reimburse costs regardless of outcome. Filing fees, deposition costs, expert witness fees, medical record retrieval — these need itemized invoices.
• The fee calculation: When the case settles or results in a judgment, provide a detailed settlement statement showing the gross recovery, your contingency percentage, deducted expenses, and the client's net recovery.
• Interim expense invoices: On cases with significant costs (medical malpractice, mass torts), send periodic expense statements so the client is not blindsided by a large cost deduction at settlement.

A settlement statement example

Item	Amount
Gross settlement	$250,000.00
Less: Attorney fees (33.3%)	($83,250.00)
Less: Case expenses
— Court filing fees	($435.00)
— Expert witness (Dr. Thompson)	($7,500.00)
— Deposition transcripts	($2,840.00)
— Medical records	($385.00)
— Mediation fee (50% share)	($1,500.00)
Total expenses	($12,660.00)
Net to client	$154,090.00

This level of detail prevents disputes and is required by ethical rules in most jurisdictions.

Split Billing and Multiple-Client Matters

Some legal work involves billing multiple clients for the same matter — joint defense arrangements, multi-party transactions, or family law matters where both parties share certain costs.

How to handle split billing

• Separate invoices: Always send separate invoices to each responsible party. Never send one invoice addressed to multiple clients.
• Allocation methodology: Document how you are splitting charges. Is it 50/50? Proportional to each party's share of the matter? Based on which tasks benefited which client?
• Confidentiality: Be careful that one client's invoice does not reveal privileged information about the other client's portion of the matter.
• Engagement letters: Your engagement letter should clearly state the billing split arrangement before work begins. Trying to sort out cost allocation after the fact creates disputes.

For matters with more than two responsible parties, create a billing allocation matrix at the outset and include it as an exhibit to each client's engagement letter.

Common Legal Invoicing Mistakes

After working with hundreds of law firms, these are the invoicing errors that cause the most payment delays and client complaints:

Block billing

Combining multiple distinct tasks into a single time entry — "Reviewed pleadings, drafted discovery requests, conferred with client regarding deposition strategy, and researched statute of limitations issue — 6.5 hours." Corporate clients will reject this outright. Break each task into its own entry.

Billing for administrative tasks

Clients should not see entries for opening a file, organizing documents into folders, scheduling meetings, or creating the invoice itself. These are overhead costs built into your hourly rate.

Inconsistent rates

If your engagement letter says the associate rate is $275/hour, every invoice should reflect exactly that. Unexplained rate changes — even small ones — destroy trust and often violate the engagement agreement.

Missing expense documentation

Billing $4,200 for "expert consultant fees" without attaching the consultant's invoice is asking for a dispute. Attach backup for any expense over a trivial amount.

Late billing

Sending an invoice three months after the work was performed is a recipe for write-offs. Clients question charges they cannot remember authorizing. Monthly billing cycles are the standard for a reason.

Ignoring billing guidelines

Corporate clients issue detailed outside counsel billing guidelines. If the guidelines say "no first-class airfare," "no charges for internal photocopying," or "pre-approve any expense over $500," those are not suggestions. Violating them delays payment and damages the relationship.

Setting Up Your Legal Invoicing Process

Here is a practical workflow for getting your billing right:

1. Record time daily: Use whatever system works for you, but do it every day. This single habit improves revenue and reduces disputes more than any other change.
2. Review pre-bills: Before sending invoices, review draft bills for vague entries, block billing, administrative tasks, and accuracy. Many firms have a billing partner review all invoices before they go out.
3. Bill monthly: Pick a consistent date — the 1st or the 15th — and invoice every active matter. Consistency trains clients to expect your invoices and plan for payment.
4. Include payment instructions: Wire transfer details, check mailing address, online payment link. Make it effortless to pay you.
5. Follow up promptly: If payment is not received within terms, follow up immediately. Our guide on late payment email templates has language specifically suited to professional service firms. You can also use KipBill's AI invoicing assistant to automate reminders and follow-ups.

For building out your invoicing workflow from scratch, our free invoice generator lets you create professional legal invoices without any setup.

Frequently Asked Questions

How should lawyers handle billing for travel time?

Most engagement letters address this directly. Common approaches include billing travel time at 50% of the normal hourly rate, billing at full rate if you are working during travel, or not billing travel time at all but passing through travel expenses. Whatever your policy, state it in the engagement letter and apply it consistently. Corporate billing guidelines often cap or prohibit travel time charges entirely.

What is the standard payment term for legal invoices?

Net 30 is the most common term for hourly billing arrangements. For retainer-based billing, the draw typically happens within 10-15 days of invoice delivery, subject to client review. Some firms offer a modest discount (2-3%) for payment within 10 days, which can meaningfully improve cash flow on large matters.

Are lawyers required to provide detailed invoices?

Yes. ABA Model Rule 1.5 requires that legal fees be reasonable, and most state bar interpretations hold that clients are entitled to invoices detailed enough to evaluate the reasonableness of the fees. This means itemized time entries with dates, descriptions, and timekeeper identification — not lump-sum statements.

How do you bill for paralegal and staff time?

Paralegal time is billable in most jurisdictions, and the U.S. Supreme Court confirmed in Missouri v. Jenkins (1989) that paralegal time should be billed at market rates rather than absorbed into overhead. Bill paralegal time with the same detail as attorney time — date, description, hours, and rate. Administrative staff time (secretarial work, filing, scheduling) is generally not separately billable.

What should a lawyer do when a client disputes an invoice?

Take it seriously and respond promptly. Review the disputed entries, provide additional detail if the descriptions were insufficient, and be prepared to make reasonable adjustments. Most state bars require lawyers to submit fee disputes to arbitration if the client requests it. Ignoring invoice disputes or threatening to withdraw from representation over billing disagreements creates ethical exposure. Document all communications about the dispute in the client file.