If you run an accounting or tax advisory practice with dozens of clients, deploying VeriFactu and B2B electronic invoicing is not just your problem — it is a problem for every single client in your portfolio. This guide explains how to handle it systematically, without losing control or multiplying your workload.
The challenge for advisors in 2026: VeriFactu, RD 238/2026 and client resistance
From 2027 onwards, every client of yours that issues invoices using software will need that software to be VeriFactu-compliant. Limited companies from 1 January, sole traders from 1 July. It is not optional.
But that is not all. Royal Decree 238/2026, which develops the B2B electronic invoicing obligation (derived from the Ley Crea y Crece), adds another layer: clients who invoice other businesses will need to do so in a structured format (XML or PDF/A-3 with embedded data), not a plain PDF. That obligation will roll out progressively, but the first wave will hit sooner than many expect.
The practical upshot for the advisory firm: over the next twelve months, every single one of your clients is going to need to change software, validate their situation, or call you with the question "what on earth is this?". If you do not have a ready answer and a clear process, that translates into hundreds of hours of unbillable support.
Client resistance is real too. Many sole traders have been using the same programme — or Excel — for years and do not understand why they need to change. The firm that explains it clearly, offers a pre-selected solution, and guides the migration turns a moment of friction into an opportunity for retention and upselling.
Options available to the accounting firm
When this moment arrives, firms typically consider one of three approaches:
Option A: each client finds their own solution
The firm informs clients of the obligation and leaves the software choice to them. Advantages: none. Disadvantages: the firm loses visibility over how clients are invoicing, receives data in inconsistent formats, and ends up troubleshooting five different programmes. Clients with less technical knowledge end up buying whatever appears first in search results — sometimes software with no verified VeriFactu certification.
Option B: the firm recommends one specific software but each client pays their own account
Better. The firm always works within the same environment, knows the data flows, can support clients efficiently. The problem is that the firm lacks a centralised view: it needs to log into each client's account separately to review anything, and the client pays directly, giving the firm fewer retention levers.
Option C: the firm manages all clients' invoicing from a single account
This is the multi-tenant model. The firm holds one account that groups all client companies. It can switch to any of them in one click, data flows consistently, and the firm can offer invoicing as a bundled service within the monthly management fee. This is the most efficient model at scale and the one that delivers the most value to both the firm and its clients.
How a multi-tenant model works for accounting firms
In a multi-tenant model, the firm is the central administrator and each client company is an independent entity within the same platform. Each company has its own data — invoices, contacts, numbering series, tax configuration — but the firm can view and manage them all from its dashboard.
In practice:
- The firm creates the main account with its own email and tax details.
- For each client, it creates a company within the account: company name, tax ID, registered address, VAT regime, invoice series.
- It decides the access level for each client: some will want to manage their own invoices (they receive a user login), others prefer the firm to handle everything (only the firm logs in).
- The firm can switch active company in two clicks, without logging out or juggling dozens of passwords.
From a regulatory compliance standpoint: each company has its own VeriFactu records with an independent hash chain. There is no mixing of data between clients. If the tax authority requests a client's records, only their records are exported.
Workflows: 3 practical scenarios
Scenario 1 — The small sole trader who wants nothing to do with technology
A self-employed plumber, 15 invoices a month to private clients and two businesses. Uses Excel, has been sending PDFs by email for years. Does not want to learn any new software.
How the firm handles it: The firm creates the company in the platform. Each month, the client sends the firm (via WhatsApp or email) the basic details of invoices issued: client, amount, description, date. The firm enters them into InvoSeal, generates invoices with QR codes and VeriFactu hash, and emails them back to the client to forward to end customers. The client never logs into the platform; the firm does everything in five minutes.
What the firm charges: Whatever it decides. The platform cost for that company is marginal within the Enterprise plan. The firm can add 15–30 euros per month to the management fee as an "electronic invoicing service", making it more profitable and increasing client stickiness.
Scenario 2 — The SME with an administrator who wants partial autonomy
A building renovation company, 8 employees, invoices other businesses (making B2B electronic invoicing relevant for them). They have an administrator who is comfortable with computers but does not want to deal with settings.
How the firm handles it: The firm sets up the company in the platform: invoice series, standard VAT rates, invoice template with the client's logo. It gives the administrator Operator access — can issue invoices and view reports, but cannot change settings or access other companies. The firm keeps Administrator access and downloads the invoice summary each month to prepare the VAT return.
Key advantage: The firm no longer needs to chase the client for invoice data at month-end. The data is directly in the platform, in exactly the format needed. That eliminates the typical chaos of "send me this month's invoices", ZIP files of PDFs with no naming convention, and last-minute corrections.
Scenario 3 — The larger company that wants full control
A company with high turnover, its own finance team, and years of experience with an ERP. They want VeriFactu for compliance but want to keep managing their invoicing in-house.
How the firm handles it: In this case the client will most likely prefer to pay for their own account. The firm can still have read-only access to review the books when needed. The firm recommends InvoSeal, assists with initial setup and data migration, and charges that onboarding as a one-off service.
Billing to the firm vs to the end client
One of the most frequently asked questions: who pays for the software?
There are two valid models:
| Model | Who pays | Advantage | Disadvantage |
|---|---|---|---|
| Firm pays | Firm (Enterprise plan for N companies) | Full control, commercial margin, client doesn't see the cost | Firm finances the cost until it passes it on |
| Client pays their account | Each client (individual plan) | Direct cost, no risk for the firm | Less control, less retention, two separate vendor relationships |
The Enterprise model works best when the firm has more than ten active clients. The volume discount more than offsets the individual cost, and the firm can add a reasonable margin to the management fee without the client perceiving it as a new cost line.
A simple numerical example: if the Enterprise plan costs €120/month for 20 active companies, that is €6 per company. If the firm charges €20 extra per client as an "electronic invoicing service", the gross margin is €14 per client. With 20 clients, that is €280 of monthly margin for something already within the normal workflow.
Training and client onboarding
The fear every firm has when rolling out something new: "How much time am I going to spend training clients?"
The answer depends on the scenario. In Scenario 1 (sole trader who doesn't want to touch anything), training time is zero: the firm handles everything. In Scenario 2, onboarding an administrator who already uses computers takes one to two hours, once.
What works in practice:
- Initial setup by the firm: The firm configures the company, imports the client's regular contact list (CSV or from the previous programme), and sets the invoice template. The client arrives at a platform that is already configured.
- Short demo session: 30–45 minutes by video call or in person. "This is how you create an invoice, this is where you see the history, this is how you download the PDF with QR." For most clients, that is enough.
- One-page reference document: A four-step PDF the client can consult independently. The firm creates it once and sends it to everyone.
- Support for questions: The typical first-two-month questions plateau. The one client who calls the most is always the same one; the rest operate on autopilot after a couple of weeks.
How InvoSeal solves this: multi-company, roles and cost sharing
InvoSeal is designed specifically for accounting and tax advisory firms to manage all their clients' invoicing from a single account. Key features:
Multi-company from the main dashboard
Once inside your account, the company selector lets you switch between all your clients in one click. No separate sessions, no need to remember each client's password, no incognito mode to manage multiple accounts simultaneously.
Differentiated roles
You can assign each client company one of three roles for their users:
- Administrator: full access (for the firm's own users or advanced clients).
- Operator: can create and send invoices, view contacts, download reports. Cannot change settings or view other companies.
- Read only: useful for managers who want to see invoicing status without modifying anything.
VeriFactu compliance per company
Each company has its own VeriFactu record chain, its own starting hash, and its own submission mode (active VeriFactu or non-VeriFactu with local record). The firm can configure each client's mode independently based on their situation.
Data export for VAT returns
InvoSeal automatically generates the input and output VAT summary by quarter, in the format needed to prepare each client's quarterly VAT return. What used to mean collecting PDFs and adding up figures in Excel becomes a one-minute download.
Integrated B2B electronic invoicing
For clients already obliged to issue electronic invoices to other businesses, InvoSeal generates invoices in the structured format compatible with RD 238/2026 standards. No extra steps: the same invoice issued normally is also generated in the required technical format.
Benefits for the practice: efficiency, upselling, control
Summarised in three dimensions every accounting firm understands:
Efficiency
The time spent chasing client invoices at the end of each quarter is one of the biggest sinks of unbillable hours in any advisory practice. When all clients invoice on the same platform the firm manages, that time disappears. The data is there, structured, ready to export.
The same applies to answering queries: if a client asks whether they issued an invoice to a particular company in February, the firm has the answer in seconds. No asking the client to search their computer, no waiting for a PDF to arrive by email.
Natural upselling
The "managed electronic invoicing" service is an easy sell because it solves a real, urgent need. Most clients don't want to think about VeriFactu, don't want to evaluate software, don't want to learn a new tool. They want their accountant to handle it. That service — which the firm can deliver with minimal additional effort once the system is set up — has high perceived value and a real margin.
Moreover, a client who invoices through the firm's platform is harder to lose: switching firms would also mean changing invoicing systems, exporting data, and setting everything up again. Retention rises naturally.
Control
Knowing in real time the invoicing status of your clients — how many invoices they have issued, whether any were rejected, whether numbering sequences are consistent — eliminates surprises at filing deadlines. Problems are spotted when there is still time to fix them, not at 11pm the night before the VAT return is due.
Frequently asked questions
Does the accounting firm need to be an official InvoSeal reseller to manage client accounts?
No. Any accounting or tax advisory firm can create a multi-company InvoSeal account and add client companies without any reseller agreement. The Enterprise plan includes multi-company access from day one.
Can the accounting firm add its own logo to client invoices?
Invoices are always issued in the client's name (their company name, tax ID and logo). The firm can customise the invoice template for each client company separately. Adding the firm's logo to a third party's invoices would be legally incorrect.
How does billing work when the accounting firm pays for the plan?
The firm pays a single Enterprise plan covering N active companies. It can pass that cost on to clients as part of the monthly management fee. InvoSeal does not issue individual invoices to each end client — the invoice goes to the firm.
What happens if a client wants to move to another software?
The client can export all their data (invoices, VeriFactu records, contacts) in standard formats at any time. There is no lock-in period or cancellation penalty.
Is VeriFactu already mandatory for accounting firm clients?
Not yet. Current deadlines are: 1 January 2027 for limited companies and 1 July 2027 for sole traders under personal income tax. Software migration takes time; getting ready in 2026 avoids the chaos of the final quarter of 2026 and first half of 2027.
Do you run an accounting or tax advisory practice and want to see how it works in practice?
InvoSeal offers demonstrations specifically for professional practices. We will show you how to configure your first client company, what the multi-company dashboard looks like and how to export data for VAT returns. No commitment required.
Request a demo for your practice →