Does the 'gastos de difícil justificación' deduction apply to me automatically?

Yes. If you're in simplified direct estimation (estimación directa simplificada), it's applied automatically and you don't need to do anything.

This reduction is calculated as 5% of your positive net income (rendimiento neto), capped at €2,000 per year. It exists to compensate for small business costs that are hard to document individually, such as minor supplies, business calls, or miscellaneous office costs.

Note that it only applies when your net result is positive, and it's incompatible with the reduction for economically dependent autónomos (TRADE).

You'll see it in your draft as "Reducción por gastos de difícil justificación.