Everyone has had this thought: what if I just do nothing? Don’t open activity, don’t issue invoices, don’t pay Social Security. What could actually happen?
The honest answer is: quite a lot. And the longer you wait, the worse it gets.
Here are the three most common scenarios — and what really happens in each.
Scenario 1: working without opening activity
Sofia started doing design work for clients. “Just a bit of extra income, not worth the hassle.” Six months later she was invoicing €2,000 a month with no activity registered.
What happens:
The tax authority cross-references data with your clients. Companies that pay you declare those payments — and the AT compares those figures against your tax history.
When the situation is detected:
- You pay IRS on everything you received (including backdated years)
- Fine for failing to register activity: between €75 and €7,500
- Late-payment interest on the tax you should have paid
The additional problem: Sofia could have been exempt from Social Security in her first year had she opened activity. By not doing so, she paid everything at once, with interest.
Opening activity is free, online, and takes 20 minutes. The cost of not having done it can be far greater.
Scenario 2: having activity but not issuing invoices
João opened his activity but never issued invoices. “Clients don’t ask, no one says anything.”
What happens:
- A client does an internal audit and requests all outstanding invoices — João has to issue them retroactively, pay the corresponding IRS, and explain the delays
- The AT can cross-reference payments clients made against what João declared — if there are discrepancies, an inspection is opened
- Working without issuing invoices is a tax infraction with fines that can reach €7,500
There is another consequence: without issued invoices, there is no income history. When João tried to apply for a mortgage, the bank asked for the last three years’ IRS declarations. There was nothing to show.
Scenario 3: not paying Social Security
Marta knew she should pay, but kept putting it off. “Too much expense, I’ll sort it out later.”
What happens:
- Debt accumulates with late-payment interest (1% per month on the outstanding amounts)
- The SS can deduct amounts owed directly from your IRS refund
- Loss of access to benefits: sickness benefit, parental leave, and contributions that do not count towards your pension
In Marta’s case, when she was ill for six weeks, she was not entitled to sickness benefit because contributions were not up to date. SS debts also appear on tax compliance certificates — which can block public procurement contracts or government work.
The maths of delay
What seems complicated now gets progressively more complicated:
| Delayed action | Cost now | Cost in 1 year |
|---|---|---|
| Open activity | 20 minutes | 20 min + retroactive fines |
| Issue invoices | 2 min per invoice | 2 min + regularisation + interest |
| Pay SS | Monthly amount | Amount + 12 months of interest |
The bureaucracy does not disappear by ignoring it. It grows.
✅ In summary
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Working without opening activity is the highest-risk scenario — the tax authority cross-references data and the retroactive consequences can far exceed what it would have cost to act in time.
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Not issuing invoices and not paying SS have concrete practical consequences — debt with interest, loss of benefits, missing income history for mortgages or contracts.
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With FIZ you open activity, issue invoices, and track obligations in one place — the work that seemed complicated fits in 15 minutes a month.
