Lieutenant Guillaume

Lieutenant Guillaume is an accounting practice on Avenue Herrmann-Debroux in Auderghem, in the Brussels region. Founded in 2015, it is registered with the ITAA under number 50.587.722 and brings together some twenty staff. The firm describes itself as created "by an entrepreneur for entrepreneurs", an origin it invokes to explain how it approaches a file: start from the owner's objectives, then work through the legal obligations.

The offering is organised in four stages the firm names itself. Create covers shaping the business model and turning assumptions into costed forecasts, for a launch or for incorporation. Automate refers to structuring the accounting flows and processing them with tooling. Manage gathers bookkeeping and routine administration: transaction processing, VAT, returns and periodic obligations. Optimise deals with the structure of the business, cost monitoring and tax, treating the company and its director together.

The office works on a real-time basis and treats that as an organisational choice: documents are collected without re-keying, processing is industrialised, and indicators are updated continuously. It names Odoo, Yuki, Horus and CodaBox, alongside automation and AI assistants for repetitive work. The practical consequence is how often the information arrives: a director who has the figures during the year can still act on the result, which is no longer true of annual accounts closed six months after the year-end.

Fees are published, which remains uncommon in the Belgian profession. The firm advertises a company subscription from 359 euros a month, built as a monthly provision calculated on document volume, the presence of staff, the sector and steering needs. That subscription includes a dedicated accountant, the VAT and intra-community returns, the periodic OSS return, the annual client listing, the tax return and the filing of the accounts, a commented and compared profit and loss statement, and a forecast budget for the following year. Fixed packages complete it: 1,285 euros to incorporate a private limited company, financial plan and representation at the notary included, 750 euros for a limited partnership, 250 euros to set up a registered office with a registered lease.

The firm provides its own application, with an invoicing module connected to the Peppol network. Since 1 January 2026, structured electronic invoicing has been mandatory between Belgian VAT-registered businesses, and an office that supplies the sending tool itself spares its client from choosing and connecting a third-party solution. The mention of the OSS return in the base subscription also signals familiarity with distance selling into other member states, a regime not every office handles.

The intended client base brings together self-employed professionals, micro-businesses and small and mid-sized companies, including companies being set up. The firm describes its role as that of an outsourced finance director: compliance and obligations on one side, financial governance and structuring on the other. That is an intermediate position, between an office limited to filings and hiring an in-house finance profile, which many businesses of this size cannot justify.

Two things set the office apart in practice. It publishes its fees as subscriptions and packages, which remains rare in the Belgian profession and allows comparison before the first meeting. And it works remotely by default, with the Brussels address serving as a meeting point rather than a required stop. For a young Brussels company looking for a single contact covering accounting, tax and steering, that combination of visible prices and connected software is a legible starting point.