How to create an invoice: complete step-by-step guide

Knowing how to create an invoice correctly is fundamental for any professional, freelancer, or business. A well-prepared invoice not only fulfills tax obligations but also projects a professional image and facilitates accounting management.

What is an invoice and why is it important

An invoice is a commercial document that reflects the details of a purchase and sale transaction. It serves as a tax receipt for both the issuer and the recipient, and is mandatory in most commercial transactions between professionals.

Issuing invoices correctly is a legal requirement that allows the Tax Agency to monitor economic activities and ensure compliance with tax obligations.

Mandatory elements of an invoice

For an invoice to be legally valid, it must contain the following data:

• Invoice number: sequential and without gaps in the numbering within each series.
• Date of issue: the day the invoice is issued.
• Issuer's details: name or company name, NIF/CIF, and tax address.
• Recipient's details: name or company name, NIF/CIF, and tax address.
• Description of products or services: a clear breakdown of what is being invoiced.
• Taxable base: the total amount before taxes.
• VAT rate applied: percentage and resulting amount.
• Personal income tax withholding (if applicable): common on invoices from professional freelancers.
• Total amount: the final amount payable.

Steps to create an invoice

1. Gather the necessary information

Before starting, make sure you have all the tax details for both yourself and the client: full name or company name, NIF/CIF, and tax address.

2. Assign an invoice number

Each invoice must have a unique, sequential number. You can use different series for different types of transactions (for example, series A for domestic clients and series B for intra-community clients).

3. Detail the invoiced items

Clearly describe the products delivered or services provided, including quantities, unit prices, and any applicable discounts.

4. Calculate the taxes

Apply the corresponding VAT rate (21%, 10%, or 4%) to the taxable base. If you are a professional freelancer, include the personal income tax withholding (usually 15%, or 7% during the first three years of activity).

5. Specify the payment terms

State the payment method (bank transfer, direct debit, etc.), the payment deadline, and bank details if necessary.

Types of invoices

Standard invoice

The most common type. It includes all mandatory data and is used in most commercial transactions.

Simplified invoice

Formerly known as a receipt, it can be issued when the amount does not exceed 400 euros (or 3,000 euros in certain sectors). The recipient's details are not required.

Corrective invoice

Issued to correct errors in a previous invoice or to record returns and price adjustments.

Summary invoice

Groups several transactions with the same client over a given period (maximum one calendar month).

Deadlines for issuance and retention

Invoices must be issued at the time of the transaction or, at the latest, before the 16th of the following month. In addition, it is mandatory to keep invoices for a minimum of 4 years for tax purposes.

Common mistakes when creating an invoice

• Forgetting mandatory details of the issuer or recipient.
• Applying an incorrect VAT rate.
• Not maintaining sequential numbering.
• Not including personal income tax withholding when it is mandatory.
• Issuing the invoice past the deadline.

How to simplify invoicing with software

Using invoicing software like Holded allows you to automate much of the process: it generates invoices with automatic numbering, calculates taxes, sends invoices by email, and maintains an organized record of all your invoicing. This reduces errors and saves time.