In short. A consulting invoice must identify both parties, carry a unique sequential number, an issue date and the period the work covers, describe the service precisely (days or deliverables, rates), show net amounts, tax and total, and state the payment terms. Clients add their own requirement, the purchase order number, without which many will not pay. In the EU and the UK, the tax treatment depends on where the client is established, and France added four new mandatory details with its 2026 e-invoicing reform.
What every consulting invoice should include
The parties
- Your company’s legal name, address and registration number, and your VAT or tax identification number where you have one.
- The client’s legal name and billing address: the entity that signed the contract, not its parent company.
- The client’s VAT number when it accounts for the tax itself (the reverse charge, in the EU).
The invoice
- A unique invoice number from a chronological, unbroken sequence.
- The issue date and the date or period the services were performed (“services for October 2026”).
- The client’s purchase order or contract reference. Rarely a legal requirement, often a condition of payment.
The service and the amounts
- A precise description: the engagement, the profile or deliverable, the number of days or units, the unit rate.
- Any discount.
- The net total, the tax rate and amount (per rate), and the gross total, with the currency.
Payment
- The due date and accepted payment methods, with bank details.
- Late-payment terms where your law or contract provides them. In France, the late-payment interest rate and a fixed €40 recovery fee are mandatory on every B2B invoice.
Three ways to bill consulting work
Time and materials: approved days × day rate
The invoice takes the days worked in the period, as recorded in the approved timesheet, and multiplies them by the day rate. The client-approved timesheet is what prevents a dispute: attach it or reference it.
| Description | Quantity | Unit price (net) | Total (net) |
|---|---|---|---|
| Senior consultant, “Financial reporting redesign” engagement, services from 1 to 31 October 2026 (timesheet approved 31/10) | 18 days | €780.00 | €14,040.00 |
| Project manager, same engagement, same period | 6 days | €950.00 | €5,700.00 |
| Net total | €19,740.00 | ||
| VAT 20% | €3,948.00 | ||
| Total due | €23,688.00 | ||
Fixed fee: by milestone or by progress
The total price is set in the contract, and each invoice bills the share that has become due: “Milestone 2, acceptance of release 1, 30% of the €120,000 fixed fee”, or “Progress at 31 October: 45%, already billed 30%, billed now 15%”. Always restate the total fee and the cumulative amount already billed, so the client can see at a glance where the engagement stands.
When billing and actual progress diverge at period end, the difference becomes accrued or deferred revenue in your accounts. We walk through the calculation in our guide to accrued revenue for consulting firms.
Rebilled expenses
Travel, accommodation and meals incurred for the engagement go on a separate line. In most VAT systems, rebilled expenses follow the tax treatment of the main service, unlike disbursements paid strictly in the client’s name, which stay outside the taxable amount. More in our article on expense rebilling.
Tax on cross-border consulting
The rules below are those of a consultancy established in France, which mirror the EU system. Other jurisdictions have their own rules, so check locally.
| Client | VAT charged | What to state |
|---|---|---|
| Business in the same country | Domestic VAT (20% in France) | Your VAT number |
| Business in another EU country | None: the client self-accounts | “Reverse charge” and the client’s VAT number |
| Business outside the EU | No French VAT | That VAT does not apply, with the legal basis |
| Private individual | Domestic VAT, as a rule | — |
France: four new mandatory details since 2026
If you invoice from a French entity, the e-invoicing reform adds four details to every invoice: the client’s SIREN number, the category of the transaction (“supply of services” for consulting), the delivery address if it differs from the billing address, and, where it applies, the statement that the company opted to pay VAT on invoicing. They are also fields of the e-invoice: a missing or wrong client SIREN can get the invoice rejected by the recipient’s platform. Payment data for services must also be reported to the tax authority, as explained in our e-reporting guide.
Six mistakes that delay payment
- No purchase order reference. Large clients’ procurement teams reject invoices that do not quote their PO.
- A mismatch with the timesheet. One billed day missing from the approved timesheet is enough to block the whole invoice.
- The wrong entity. Billing the parent instead of the subsidiary that signed means a credit note and a new invoice.
- A fixed fee with no running total. Without the total fee and the amount billed to date, the client has to rebuild the history before approving.
- The wrong VAT for a foreign client. Charging domestic VAT to an EU business produces an incorrect invoice the client cannot deduct.
- Invoicing late. Payment terms run from the issue date: every day you wait to invoice is a day of cash lost.
Producing these invoices without re-keying
In AlibeeZ, the billing model (time and materials, capped time and materials, milestone, progress) belongs to the contract, along with its payment terms, VAT and currency. Invoices are generated from approved time and expenses: the billed days are the timesheet’s, a fixed fee’s running total is calculated, and expenses come in from expense reports. Mandatory details come from client and company records filled in once. See billing models in AlibeeZ.
Frequently asked questions
What should a consulting invoice include?
Both parties’ legal details and tax numbers, a unique sequential number, the issue date and service period, a precise description with quantities and rates, net amount, tax and total, the due date and payment terms, plus the client’s purchase order reference.
Do I charge VAT to a client in another country?
Not to a business client in another EU country: the client self-accounts under the reverse charge and the invoice states “Reverse charge”. For a business outside the EU, a French consultancy charges no French VAT. Private individuals are generally charged domestic VAT.
Should I attach the timesheet to a time-and-materials invoice?
It is rarely mandatory, but it is the surest way to avoid a dispute: the client checks that the billed days are the ones it approved.
How do I invoice a fixed-fee consulting engagement?
By milestones or by progress, stating on each invoice the total fee, the share billed now and the cumulative amount already billed.
What payment terms can I set?
Those in your contract, within local law. In France, B2B payment terms are capped at 60 days from the invoice date, or 45 days end of month if agreed.
