Self-employed contribution by real income: how it's calculated and what to pay each month
If you’re self-employed in Spain, your Social Security contribution is one of the most significant fixed costs of your activity. What you might not fully understand is how it’s calculated: why it can change from one year to the next, what it has to do with your invoicing, and why an unexpected adjustment letter sometimes arrives.
The answer lies in the contribution system based on real income, which links your monthly contribution to what you actually earn as a self-employed worker — not a freely chosen base. Understanding how it works is the key to paying the right amount every month and avoiding surprises at the end of the year.