Self-Employed Contributions Based on Real Income: Brackets, Base Changes and TGSS Adjustments

Since 2023, what self-employed workers in Spain pay in social security contributions no longer depends on a base they simply pick at will, but on their actual net income. The system is still fully in force in 2026 and raises plenty of questions: Which bracket am I in? Can I change my base? Why am I getting a letter from Social Security a year later? Let’s go step by step.

How the bracket system works

The regulation sets out a table of monthly net income brackets, and each bracket has a minimum and a maximum contribution base. You choose a base within the range for your bracket, and the current contribution rate is applied to it. The exact figures in the table are updated by law, so always check them on the Social Security website or in the Budget Law for the current year.

What is net income? It isn’t your revenue, but what is left after subtracting your deductible expenses. An additional deduction is also applied for hard-to-document expenses (generally 7% for self-employed individuals and 3% for those who work through a company). The result is then divided by twelve to get the monthly figure used to find your bracket.

Example with round numbers: a self-employed worker invoices €36,000 a year and has €12,000 in deductible expenses. Their income before the deduction is €24,000. Applying the 7% leaves €22,320, which is €1,860 a month. That monthly amount is what gets compared against the bracket table to determine which one they fall into.

When you register, you have no track record: you must estimate your income for the year. It is a forecast, not a commitment, but it pays to be realistic, because it will later be checked against reality.

Base changes: when and how many times

Since business activity isn’t steady, the system lets you adjust your base several times a year (up to six), with effect from dates set by the regulations and always by applying before the relevant period begins. You can do it through the Social Security electronic office or through your accountant.

A few practical tips:

• If your income is rising steadily, raise your base accordingly and you’ll avoid a big surprise at the adjustment.
• If you’ve had a bad half-year, lower it within the limits of your new expected bracket.
• Review your forecast every quarter, taking advantage of the VAT and income tax close: the numbers are already in front of you.

The TGSS after-the-fact adjustment

This is the part that surprises people most. When the year ends, the Treasury of the Social Security (TGSS) cross-checks its data with what it receives from the Tax Agency about your actual income for that year. It then compares the base you contributed on with the one that would have applied based on that income, and two situations can arise:

• You contributed too little: the TGSS claims the difference, which you must pay within the period stated in the notification.
• You contributed too much: the excess is refunded automatically, without you having to ask for it.

The adjustment arrives the following year, once you have filed your income tax return, and is usually notified electronically. That’s why it is important to have electronic notifications enabled and to check your mailbox: missing the payment deadline carries surcharges.

Common mistakes

• Estimating income “by eye” and not updating your base during the year.
• Confusing revenue with net income: well-documented expenses lower your bracket, but only if they are genuinely deductible.
• Not setting money aside for the adjustment: if you contributed below your actual bracket, the difference can be considerable. Put a portion aside every month.
• Forgetting that the tables change: the regulations provide for periodic revisions; don’t rely on figures from previous years.

At Zythos Business we support self-employed professionals and small businesses with decisions like these: we project your income with up-to-date accounting, let you know when it makes sense to adjust your base and help you anticipate the effect of the adjustment, so that your contribution is fair and you get no surprises.