From new consulting firm to first paid invoice: a one-day setup guide

The gap between starting a consulting engagement and actually getting paid is mostly administrative. The work itself — the expertise, the advice, the deliverables — that's what you were hired for. But invoicing is what converts that work into money in your account, and for most new consultants, it's an unfamiliar process with just enough moving parts to delay the first payment by weeks.

This guide covers everything you need to send your first professional invoice and get paid, in order. Most people can do all of this in a single day.

The five things you need before you can invoice

Before you send anything, you need five pieces of information confirmed and written down:

Your firm details. Legal name, trading name if different, registered address, contact email, and — if you're VAT-registered or registered for GST/HST — your tax registration number. If you're operating as a sole trader, your personal name and address are the firm details. If you've incorporated, use the company name and registered office.

Your client's details. Their full legal name (not just the contact's name), billing address, and the email address invoices should go to. For B2B invoicing, the billing contact is often not the person you work with day to day — ask explicitly. If they're VAT-registered and you're in the UK, get their VAT number too.

A description of the service. This is the line item on the invoice. "Consulting services — May 2026" is technically sufficient but "Strategic communications advisory — April engagement per SOW dated 2026-03-15" is better. The more specific the description, the fewer questions your client's accounts payable team has, and the faster the invoice moves through their approval process.

Your rate and the amount owed. Whether you're billing a fixed fee, an hourly rate multiplied by hours worked, or drawing down a retainer, you need the number agreed and the calculation clear. If you're billing hours, have the hours logged and ready to show.

Payment terms. Net 30 is standard for professional services — payment due 30 days from invoice date. Net 14 is becoming more common and is reasonable to ask for, especially from smaller clients or for smaller amounts. Some clients will push back; most won't. Whatever you agree, put it on every invoice.

Invoice numbering: start the habit on day one

Invoice numbers seem trivial but they matter for three reasons. First, they make it easy to reference a specific invoice in conversation ("can you check on INV-0042?"). Second, your accounting records need them. Third, HMRC and many other tax authorities require invoices to be sequentially numbered — gaps in the sequence can trigger questions in an audit.

Pick a format and stick to it. INV-0001 is fine. 2026-001 (year-sequence) is also common and makes it easy to tell at a glance which year an invoice is from. Don't restart the sequence each year unless you use the year prefix. Whatever you choose, the first invoice is the hardest to set up; every one after that is just incrementing a number.

What goes on the invoice

A professional invoice for consulting services needs:

Your firm name and address. Your client's name and address. The invoice number. The invoice date. The due date (invoice date plus your payment terms). A line-item description of the service. The quantity and rate if applicable (e.g. 8 hours × £150/hr). The subtotal. Any applicable tax (VAT at 20%, GST at 5%, etc.) shown as a separate line with the rate and amount. The total amount due. Your payment details — bank name, account number, sort code or routing number, IBAN and BIC if the client is in another country.

That's the complete list. Everything else is optional. A logo and some formatting makes it look more professional; a thank-you note in the footer is a nice touch. But the above is what makes it a legally valid invoice.

Sending the invoice

Send it as a PDF attachment, not in the body of the email and not as an editable file. PDFs can't be accidentally modified, they print consistently, and they're what accounts payable teams expect.

The email should be short. Something like: "Please find attached invoice INV-0001 for £2,400 in respect of [service], due by [date]. Please don't hesitate to get in touch if you have any questions." That's it. No need for a long explanation; they know what they hired you for.

Send it to the billing contact, not your day-to-day contact, unless they're the same person. CC your day-to-day contact so they know it's in the system. Some larger clients require invoices to go through a supplier portal rather than email — ask before you send if you're not sure.

Setting up a follow-up reminder

The most common reason consulting invoices go unpaid past their due date is not that the client is unwilling to pay — it's that the invoice got lost in someone's inbox, sat in an approval queue, or was filed under the wrong project code. A single polite follow-up email resolves most of these.

The problem is remembering to send it. When you're running an engagement, chasing invoices is the last thing on your mind. Set a calendar reminder for the day after the due date so that if payment hasn't arrived, you send a short follow-up that day — not a week later. "Just following up on INV-0001, due yesterday. Happy to resend if helpful." That's sufficient for a first chase.

If the invoice is still unpaid after a second reminder a week later, a phone call is usually more effective than a third email. The issue at that point is almost always internal — the invoice is stuck somewhere — and a call gets it unstuck faster.

Automated payment reminders, where the system fires the follow-up email on a schedule without you having to remember, are one of the more valuable features in modern invoicing software. They're not essential for your first client, but once you have four or five active invoices at different stages, manual reminder tracking becomes error-prone.

What a one-day setup looks like

Morning: confirm your five pieces of information, choose an invoice format (even a clean Word template works for the first one), set up your invoice numbering sequence.

Midday: draft the invoice, double-check the maths and the due date, save it as a PDF.

Afternoon: send it to the correct billing contact with a brief covering email, save a copy in your records, set a calendar reminder for one day after the due date.

That's the full first-invoice workflow. The tools you use matter less than having the information right and sending it promptly. Delays in invoicing are delays in getting paid — the sooner the invoice is in your client's system, the sooner it moves through their approval cycle.

Once you're running more than two or three active client relationships, the manual parts of this process — generating PDFs, tracking due dates, sending reminders — are worth automating. At that point, software that handles the invoicing cycle end-to-end starts paying for itself in time saved per billing cycle.