When to send an invoice
Send an invoice as soon as the work or milestone is complete, or on the schedule you agreed with the client. The sooner the invoice lands, the sooner the payment clock starts, so do not let it sit for days. For one-off projects, invoice on delivery or when you hit an agreed milestone. For ongoing work, pick a rhythm and stick to it: a fixed day each month, or after a set number of hours.
If a project is large, agree a deposit or staged payments up front so you are not financing the whole job yourself. A common pattern is a percentage on signing, a percentage at the midpoint, and the balance on completion. Always confirm the amount, scope and due date before you start, then the invoice simply documents what was already agreed.
How to number invoices sequentially
Every invoice needs a unique, sequential number. This is not optional in most countries: tax authorities expect an unbroken sequence with no gaps or duplicates, because gaps suggest a hidden or deleted invoice. The simplest scheme is a plain running number that increments by one each time. Many freelancers prefix it with the year or a client code, for example 2026-001, 2026-002, and so on.
Pick one scheme and keep it consistent for the whole tax year. Do not reset the counter mid-year, skip numbers, or reuse a number from a cancelled invoice. If you void an invoice, leave its number retired and issue a credit note rather than deleting it. A generator that assigns the next number automatically removes the main risk: accidental gaps and duplicates from manual numbering.
What to put on a freelancer invoice
A valid invoice has to identify who is billing whom, for what, and how much. The exact wording varies by country, but the core fields below are expected almost everywhere. If you are VAT-registered, add the VAT-specific items described in the next section.
- The word "Invoice"
- Clearly label the document so it is not mistaken for a quote, estimate or pro forma.
- Invoice number and date
- A unique sequential number and the date the invoice is issued.
- Your details
- Your trading name or legal name, address, and any business or tax registration number that applies.
- Client details
- The client's name (or company name) and address, and their VAT number where the reverse charge applies.
- Description of work
- A line for each service or deliverable, with quantity or hours, the unit rate, and the line total.
- Amounts
- The subtotal, any tax, any discount, and the total amount due in the agreed currency.
- Payment terms and due date
- When payment is due (for example net 14 or net 30) and how to pay, including bank or transfer details.
- A reference, if the client needs one
- A purchase order or project reference that lets the client route the invoice for approval.
Handling VAT and tax as a freelancer
Whether you charge tax depends on whether you are registered. If you are not VAT- or sales-tax-registered, you simply bill your fee with no tax line, and your invoice total is the amount the client pays. Many freelancers operate below a national registration threshold and never charge VAT at all. You are still responsible for declaring this income as profit on your own tax return, so keep every invoice.
If you are VAT-registered, you must show your VAT number, the net amount, the VAT rate and the VAT amount, and the gross total. For cross-border business-to-business work inside the EU, the reverse charge usually applies: you invoice with no VAT, show both parties’ VAT numbers, and add a „Reverse charge“ note so the client accounts for the tax in their own country. Verify the client’s VAT number before zero-rating, and remember that the income tax on your profit is separate from any VAT you collect and pass on.
Setting payment terms
Payment terms tell the client exactly when the money is due. State them on every invoice and in your contract. The most common terms are net 14 and net 30, meaning payment is due 14 or 30 days after the invoice date. Shorter terms get you paid faster; some freelancers use due on receipt for small jobs or new clients.
Spell out the practical details too: the currency, the accepted payment methods, and any late-payment fee or interest you will apply if the due date passes. Many jurisdictions give a legal right to charge interest on overdue commercial invoices, so a clear clause is both fair and enforceable. Setting terms up front prevents the awkward conversation later and gives you firm ground to chase from.
Chasing late payment and keeping records
When an invoice goes past due, follow up promptly and professionally. A short, polite reminder on the day after the due date resolves most cases: many late payments are simple oversights. If that is ignored, escalate in stages: a firmer reminder, a phone call, then a formal notice referencing your late-payment terms and any interest due. Keep the tone businesslike; you want to be paid and keep the client.
Keep a copy of every invoice you issue and receive, along with proof of what was delivered and when payment arrived. Retention periods are set nationally and are commonly between 5 and 10 years. Good records make your tax return painless, back you up in any dispute, and let you see at a glance which invoices are still outstanding.
Frequently asked questions
Do I need to be a registered business to send an invoice?
No. In most countries a sole trader or freelancer can issue invoices under their own name without forming a company. You do need to declare the income on your tax return, and you may need a tax or business registration number on the invoice depending on your country and turnover.
How do I number my invoices?
Use a unique, sequential number that increases by one with each invoice, with no gaps or duplicates. A simple running number works, and many freelancers prefix it with the year, such as 2026-001. Keep the sequence consistent and never reuse or delete a number; void with a credit note instead.
Do I have to charge VAT as a freelancer?
Only if you are VAT-registered. Many freelancers stay below their country's registration threshold and bill with no VAT line. If you are registered, show your VAT number, the rate and the VAT amount, and apply the reverse charge for cross-border B2B work inside the EU. Income tax on your profit is separate from VAT.
What payment terms should I set?
Net 14 or net 30 are the most common, meaning payment is due 14 or 30 days after the invoice date. Shorter terms, or due on receipt, get you paid faster, especially with new clients. State the term, the currency, the payment method and any late-payment interest clearly on every invoice.
What can I do if a client pays late?
Send a polite reminder the day after the due date, then escalate with a firmer reminder, a call, and a formal notice citing your late-payment terms. Many jurisdictions let you charge interest on overdue commercial invoices, so reference that clause if you included one in your terms.
How long should I keep my invoices?
Retention periods are set by each country and are commonly between 5 and 10 years. Keep both the invoices you issue and the ones you receive, plus proof of delivery and payment, so your records support your tax return and any dispute.