Billing tools for project-based invoicing compared in 2026

For companies working on a project basis—consultancy, IT, marketing, architecture, engineering—invoicing is not a simple matter of putting an amount on an invoice. You invoice hours at different rates, per employee, per project phase, including expense claims and mileage. This complexity makes manual invoicing error-prone and time-consuming.

In this article, we compare invoicing tools for project-based invoicing and show how tools automate invoicing based on recorded hours.

Key insights

• Project-based invoicing differs fundamentally from standard invoicing. Multiple rates, contract types, and approval flows make it complex.
• Tools that automate invoicing based on recorded hours prevent the biggest source of error: manual retyping.
• There are two approaches: standalone invoicing software and integrated time tracking with invoicing. For project-based companies, the integrated approach is almost always more efficient.
• The faster you invoice, the faster you get paid. Platforms for sending accurate invoices faster shorten the time between approval and payment.
• E-invoicing via Peppol is becoming the European standard. In Belgium as of January 1 already mandatory for B2B by 2026.
• A client portal reduces discussions and accelerates approvals.

What makes project-based billing special?

With project-based billing, you face challenges that do not arise with standard billing. The complexity lies in multiple rate structures, different contract forms, and approval requirements.

• Multiple rate structures: a senior consultant bills at a different rate than a junior, on-site work differs from remote work, overtime is sometimes billed at 150%
• Different contract forms: time & materials, fixed fee, prepaid card, or retainer — your tool must be able to handle all these models
• Time specification: clients expect a detailed overview of who worked how many hours on which tasks, when, and how often.
• Expense claims and travel costs: in addition to hours, mileage and material costs must also appear on the project invoice.
• Approval before invoicing: hours must first be approved internally and by the client.

Why is this relevant for consultancy and IT?

At consultancy and IT firms, all these complexities come together. You work with changing teams, changing clients, and changing rates—often simultaneously. A senior architect at €180 per hour working two hours on client A and four hours on client B, while a junior consultant at €95 per hour is on the same project: this must appear flawlessly on two different invoices.

In the case of secondment, hirer's remuneration also plays a role. As of July 1, 2026, equivalent pay is legally enshrined. Therefore, rate structures must not only be correct per employee and project, but also align with the employment conditions at the hiring company.

What should you look for when choosing a tool?

When comparing billing tools for project-based billing, these functionalities are the most important.

Automatic hours-to-invoice conversion

The core of project-based billing: approved hours are converted into invoice lines with a single click. No manual intervention.

Flexible rate structures

You must be able to set rates per employee, per project, per client, and per task type. Overtime rates and tiers must be configurable.

Quote-to-project-to-invoice flow

The ideal flow: create a quote, have the client sign digitally, convert the quote into a project, record hours, and invoice automatically. All in one system.

Client portal

A portal where the client has real-time insight into hours and costs. This reduces the number of discussions and speeds up approvals.

Integration with accounting

The invoice must appear in your accounting package as a sales entry with a single click. Manual retyping is a source of error.

E-invoicing

E-invoicing via Peppol is becoming the European standard. In Belgium, this is mandatory for B2B transactions as of 1 January 2026.

📚 Read all about e-invoicing, UBL invoices, and Peppol here.

What can you do now?

• Inventory how many different rate structures and contract types you currently use
• Calculate how much time your team spends per month creating invoices
• Check if your current tool can automatically convert approved hours into invoice lines

Standalone invoicing software vs. integrated time tracking

There are two approaches: you can choose standalone tools or an integrated system. Which approach works best depends on your business structure and growth.
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Standalone invoicing software such as Moneybird, WeFact, or e-Boekhouden. These tools excel in invoicing and accounting but have limited or no time tracking functionality. You need two systems and must transfer data manually or via an integration.
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Integrated time tracking and invoicing such as TimeChimp, Simplicate, or Gripp. These are tools that automate invoicing based on recorded hours: time tracking, project management, and invoicing in one system. Hours are automatically converted into invoice lines, without export or import.
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The following table provides an overview:

• Hours to invoice: Manually or via integration. Automatic, one click.
• Rate management: Limited. Per employee, project, or client.
• Project insight: None or limited. Real-time budgets and progress.
• Accounting: Extensive built-in. Via integration (Exact, Twinfield, AFAS).
• E-invoicing: Varies. Peppol and UBL.
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In short: for project-based companies, the integrated approach is almost always more efficient. The automated flow from time to invoice eliminates the biggest source of error and saves the most time.

Platforms for sending accurate invoices faster

The faster you invoice, the faster you get paid – this is directly linked to your cash flow. In practice, for many companies, it takes weeks before hours appear on an invoice. The causes: hours are not approved, the project manager lacks an overview, or creating the invoice takes too much time.

With an integrated tool, you can invoice immediately after approval. That means: fewer days between approval and payment, fewer outstanding items, and a healthier cash flow.

Note: with the rise of mandatory e-invoicing, invoices are also processed faster by the recipient. Paper invoices or PDFs via email will no longer be accepted for B2B in Belgium after January 1, 2026.

TimeChimp: invoicing tools for project-based invoicing

We see that project-based companies switching to an integrated system not only invoice faster, but also more accurately. We see the best results at companies that complete all steps – from hour to payment – ​​in a single system.

• Automatic invoicing: from approved hours to sent invoice in thirty seconds
• Flexible rates: per employee, per project, per client — including overtime rates
• Quote-to-project flow: from quote to project to invoice in one system
• Client portal: your client has real-time insight into hours and project progress
• Expense claims and mileage: automatically on the invoice next to the time lines
• Approval flows: internal and external, with one click
• E-invoicing via Peppol: send e-invoices that comply with the European standard
• Accounting integrations: synchronize with Exact Online, Twinfield, AFAS or Yuki
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💡 View how invoicing works in TimeChimp here.

Conclusion

Project-based billing requires a tool capable of handling the complexity of multiple rates, contract types, and approval workflows. The most efficient approach is an integrated system that combines time tracking and invoicing.
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✔️ Choose a tool that automatically converts approved hours into invoice line items

✔️ Ensure flexible rate structures per employee, project, and client

✔️ Use a client portal to speed up approvals

✔️ Check if the tool supports e-invoicing via Peppol

✔️ Choose a tool that integrates with your accounting software
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👉Looking for project-based billing tools that help you send accurate invoices faster? Try TimeChimp free for 14 days.