Invoicing Your First Client: A Beginner's Guide for New Freelancers

The excitement of landing a first client often means the invoice itself gets rushed together at the last minute — and that's exactly when small but important details get missed. A few things trip up new freelancers again and again:

• Missing KVK and VAT numbers. Every invoice you send as a registered business must show your Chamber of Commerce (KVK) number and your VAT number. Leaving either off isn't just sloppy — it makes the invoice legally incomplete, which can cause problems for you at tax time and for your client if they want to reclaim VAT.
• Incorrect or inconsistent invoice numbering. Your very first invoice needs a number, and every invoice after it needs to follow in a unique, sequential, gap-free order. Freelancers who start numbering casually (or restart numbering by client) often run into trouble later when the Belastingdienst expects a clean, traceable sequence.
• No clear payment terms. An invoice without a stated due date leaves room for ambiguity — and ambiguity is how first invoices end up paid late, or not followed up on at all.

If you want the full picture of what belongs on a compliant Dutch invoice, our complete guide to creating invoices as a freelancer walks through every required field in detail. Getting it right on invoice number one saves you from having to correct a pattern later across dozens of invoices.

The best time to settle payment terms isn't when you send the invoice — it's before you start the assignment. Waiting until the work is finished to bring up when and how you expect to be paid puts you in a weak negotiating position and increases the odds of a misunderstanding.

Before you begin, make sure you and your client agree on:

• The payment term, typically 14 or 30 days after the invoice date. Shorter terms are entirely reasonable for a new client relationship, especially your first one.
• The payment method, usually a straightforward bank transfer, and whether you'll include your IBAN directly on the invoice.
• Whether a deposit is required, particularly for larger projects or clients you don't yet have a track record with.
• What happens with expenses or extra work, if the scope of the assignment might change along the way.

The easiest way to lock all of this in is to put it in a written quote and get it approved before work starts, rather than relying on a verbal agreement. slimzaak's quotes feature lets you set out your price and payment terms clearly, get the client's sign-off, and then convert the approved quote straight into an invoice — so the terms you agreed on at the start are exactly what shows up on the bill at the end.

For a brand-new client, your invoice is often the second document they see from you — after the quote — and one of the few pieces of paperwork that puts your business name in front of them directly. A generic, inconsistent, or hand-typed invoice quietly signals that you're still figuring things out. A clean, branded template signals the opposite: that you run things properly, invoice after invoice.

A professional invoice template typically includes your logo, consistent colors and layout, and all the legally required fields laid out clearly — so nothing looks improvised. That consistency matters twice over: it builds confidence with the client paying you right now, and it makes every future invoice to that same client (or a referral they send your way) instantly recognizable as coming from you.

This is especially worth getting right if you expect to send invoices regularly, whether manually per project or automatically from recurring orders. slimzaak supports both: you can create manual invoices and quotes for one-off assignments, or set up automatic invoices that generate themselves from webshop or marketplace orders, all using the same branded template so your invoicing looks consistent no matter how it's triggered.

Sending the invoice isn't the finish line — a first invoice to a new client is also the first real test of how smoothly they pay. Don't assume silence means everything is fine; a light-touch follow-up habit from the very start keeps small delays from turning into real problems.

A simple rhythm works well for most freelancers:

1. A few days before the due date, a short, friendly note confirming the invoice is on its way to being due is enough for most clients — not pushy, just a nudge.
2. On or shortly after the due date, if payment hasn't arrived, send a polite reminder referencing the invoice number and due date, and ask if there's anything holding it up.
3. One to two weeks past due, if there's still no response, a firmer written reminder is appropriate, restating the amount, the original due date, and a new deadline.

For a first-time client, err on the side of a friendly, professional tone before assuming the worst — payment delays are often genuinely accidental, especially for small businesses juggling their own admin. If a reminder doesn't get a response and the invoice stays unpaid, our guide on sending a payment reminder and formal demand letter covers the next steps, including when to escalate to a formal aanmaning.

Getting all of this right by hand — correct legal fields, sequential numbering, a branded look, and a system for chasing overdue payments — is a lot to manage manually when you're also trying to do the actual client work. slimzaak is built to handle the invoicing mechanics so you can focus on that.

With slimzaak, you can create manual invoices and quotes for individual clients, with your KVK and VAT number, correct sequential numbering, and payment terms filled in automatically every time. If you sell through a webshop or marketplace, automatic invoices are generated straight from incoming orders, so nothing gets missed once volume picks up. The built-in template designer lets you apply your own logo and branding once, so every invoice — manual or automatic — looks consistently professional from your very first client onward. And when you've agreed on a price with a quote, converting it to an invoice takes one click, with the same terms carried over automatically.

All of this is available on slimzaak's Free ZZP plan: €0 per month, up to 250 invoices a month, and no credit card required to get started. For general guidance on running a business in the Netherlands as a freelancer, including your registration and tax obligations, business.gov.nl is a useful official reference to keep alongside your own invoicing setup.