Law Firm Success Fees: How to Calculate, Record and Invoice Contingency Fees

A success fee is the part of a lawyer's fee that depends on the outcome — usually a percentage of the amount recovered or saved. It is attractive to clients who cannot fund a long dispute, and it can be the most profitable work a firm does. It is also where the worst fee disputes come from, because two things that seemed obvious when the agreement was signed turn out not to be: when the fee became payable, and what it is a percentage of.

This guide covers how to define both, how to calculate the fee, how to combine it with a fixed fee, and how to record and invoice it so the client can check every number.

This is general guidance on running a practice, not legal or tax advice. Whether a success fee is permitted, and on what conditions, depends on your country and your bar rules — in Saudi Arabia, for example, start with the Saudi Bar Association. Check before you offer one.

The short answer

To calculate a success fee: identify the success event named in the agreement, take the base amount the agreement defines (for example, the principal actually collected, excluding court costs), multiply by the agreed percentage, subtract anything the agreement says is credited against it, then add VAT at the applicable rate. Each of those five inputs should be written in the fee agreement before work starts.

Step 1: Define the success event

"If we win" is not a definition. Common success events, from earliest to latest:

• A first-instance judgment in the client's favour.
• A final judgment after appeal, or the end of the appeal period.
• A signed settlement, in or out of court.
• Money actually received — through voluntary payment or enforcement.

The difference matters. A judgment for AED 2 million that is never enforced is a success on paper and nothing in the client's account. If the fee is payable on judgment, the client may owe a fee on money they never see. If it is payable on receipt, the firm carries the enforcement risk. Either can be fair — but the agreement has to say which, and what happens on partial recovery.

Step 2: Define the base amount

"A percentage of the claim" invites argument. State whether the base is:

• the amount awarded or the amount collected;
• the principal only, or principal plus interest and compensation;
• before or after court fees, expert fees and enforcement costs are reimbursed;
• in the case of a defence, the amount saved — measured against what figure.

Step 3: Combine it with a fixed element (hybrid agreements)

Pure success fees are rare. More common is a hybrid: a fixed or retainer fee paid in stages, plus a lower success percentage. The agreement should say whether the fixed fee is credited against the success fee or added to it. Those two readings can differ by a large sum, and it is the single most common ambiguity in hybrid agreements.

A worked example

A commercial claim with a hybrid agreement: AED 30,000 fixed fee payable in two stages, plus 10% of the principal collected, with the fixed fee not credited. The court awards AED 1,200,000 principal and AED 80,000 compensation; the client collects the principal in full.

• Base amount: AED 1,200,000 (principal collected; compensation excluded by the agreement)
• Success fee: 10% × 1,200,000 = AED 120,000
• VAT at the UAE standard rate of 5%: AED 6,000
• Success-fee invoice: AED 126,000, in addition to the AED 30,000 already invoiced in stages

Had the fixed fee been credited, the success fee would be AED 90,000 before VAT. Same case, same percentage, AED 30,000 difference — decided by one sentence.

Step 4: VAT and e-invoicing

A success fee is a fee for legal services, so it is normally subject to VAT like any other fee: 5% standard rate in the UAE, 15% in Saudi Arabia. Show it on the invoice as its own line. If your firm is within an e-invoicing regime — such as ZATCA's in Saudi Arabia — those requirements apply to success-fee invoices too. Confirm your obligations with your tax adviser or the UAE Federal Tax Authority.

Step 5: Record time even on success-fee matters

You will not bill those hours, but without them you cannot tell whether your success-fee pricing is working. A 10% fee that took 900 hours to earn may be worse business than an hourly matter. We covered where recorded time goes missing in another guide.

Step 6: Invoice so the client can check every number

The success-fee invoice should let the client reproduce the figure without calling you: the success event and its date, the base amount and where it comes from, the percentage, any credits, and VAT. Attach or reference the judgment, settlement or receipt that triggered it. Disbursements — court fees, expert fees, translations — go on separate lines; they are reimbursements, not fees.

How Smart Legal OS handles this

Smart Legal OS does not calculate a success fee for you when a judgment is entered — that calculation depends on the wording of your agreement, and it should be made by the lawyer. What it does is keep every input on the matter:

• Each case has a billing type — hourly, flat fee, contingency, retainer or pro bono — and for contingency cases the agreed percentage is recorded on the case and shown on the case page.
• Time is recorded against the case with a timer or manual entry, so you can see the hours behind a success fee.
• Invoices take manual lines for the success fee and each disbursement, plus lines generated from time entries, with the tax rate you set.
• Client funds (trust) accounts hold money received for the client and can pay an invoice directly; a payment larger than the balance is refused.
• Clients pay by card in the client portal, and every invoice change and payment is written to the firm's audit trail.

For the other fee models and a full billing routine, see how to calculate law firm fees. See the full feature list or compare plans — there is a 14-day free trial with no credit card.

Frequently asked questions

When does a success fee become payable? When the success event written in the fee agreement happens — for example a final judgment, a signed settlement, or receipt of the money. If the agreement does not say, expect a dispute; define it before work starts.

Is a success fee calculated on the amount awarded or the amount collected? Whichever the agreement says. Calculating on the amount collected protects the client from paying a fee on an unenforced judgment; calculating on the amount awarded protects the firm from enforcement risk.

Is the fixed fee deducted from the success fee in a hybrid agreement? Only if the agreement says it is credited. State it explicitly — "credited against" or "in addition to" — because the difference is often large.

Do I charge VAT on a success fee? Normally yes, as on any legal fee: 5% in the UAE and 15% in Saudi Arabia at the standard rates. Confirm the treatment of your own engagements with a tax adviser.

Can software calculate success fees automatically? It can store the percentage and the figures, but the calculation depends on how your agreement defines the success event and base amount. In Smart Legal OS the percentage is recorded on the case and the lawyer adds the success-fee line to the invoice.