Invoicing occasional work of €500 to €800 without paying self-employed contributions

Earning €800 a month on the side: the multiple-jobs maze

Earning between €500 and €800 a month from occasional work shouldn't be an accounting problem. It becomes one the moment the company paying you can no longer hand over cash and demands an invoice. That's the situation of an employee used to getting paid extras off the books who suddenly discovers that to keep receiving those amounts, they need paperwork, a stamp and a tax number.

The question is straightforward: is there a way to invoice those amounts without the system swallowing them? Their own estimate, after looking into it, is that they would lose around 70% of what they invoice in taxes and contributions. The figure is a personal calculation, not an official statistic, but the order of magnitude explains why legally holding multiple jobs is such a bitter pill.

What registering costs and why the first year is misleading

As pointed out in the thread, invoicing on a recurring basis without registering with the RETA (Spain's self-employed social security scheme) wouldn't be viable except in specific cases, such as retirees giving lectures or artistic activities. For everyone else, Social Security takes its cut. The consolation is the flat-rate scheme for the self-employed, which participants put at around €80 or €90 a month for the first two years. With income of €500 to €800, those numbers add up.

The problem comes later. Once the discounted period ends, the contribution rises regardless of what you invoice, and there the €500 cloud turns to fog. Income tax is added to the payer's withholding: some recommend applying the 15% rate instead of the 7% for new self-employed workers, to avoid a nasty surprise when it's time to file the annual return.

The contribution that doubles and the one-off invoice cap

There's a nuance almost nobody calculates correctly. If you're already paying contributions through the payroll of your main job, your self-employed contribution isn't added on top: you pay the higher of the two and lose the other. Having multiple jobs doesn't spread the burden; it partly doubles it.

There is a middle path for genuinely occasional work. A private individual not registered with any scheme can issue a one-off invoice of up to around €1,500, according to circulating estimates, though the range depends on current regulations. The key word is occasional: repeating it month after month with the same client stops being a one-off and becomes a regular activity, which requires registering.

Invoicing cooperatives and the antiestéticar of the boss

The most frequently mentioned alternative is invoicing cooperatives, designed precisely for one-off jobs. They work, but they're no magic: they register you as a worker, which in theory would have to be reported to your main employer. That's the real sticking point. The antiestéticar is that any blockage or dip in performance will be blamed on the second job.

Have they been banned? No. There have been shutdowns over bad practices, but the arrangement remains legal. What no cooperative solves is the underlying risk some point to: always invoicing the same payer can end up splashing back onto that company, which under that reading should be hiring you directly.

Under these rules, the only arithmetic that fully adds up is giving up the extra income or staying off the books. Nobody has found a third path the tax authorities would applaud. The rest are calculations that hold up until the first inspection or the first payslip with withholding.