I compared three years of IRS declarations my accountant filed. Here's what I actually learned.

My accountant charges per annex. One Modelo 3 declaration plus four annexes costs about 500 euros a year. I've been paying that since 2022.

This year I sat down and compared all three declarations side by side. Same person, same activity code, same regime simplificado, same family. What I found were three different filing approaches across three years, and a set of questions I'd never thought to ask.

The headline number I paid barely moved when I finally understood what was going on. That's the point. This isn't about second-guessing your accountant. It's about finally understanding your own situation.

What changed when nothing changed

In 2022, my declaration had three annexes: Anexo B (self-employment income), Anexo L (non-habitual resident regime), and Anexo SS (Social Security). Ten pages total.

In 2023, it grew to four annexes. Anexo J appeared for the first time, declaring foreign income from Sweden and the Netherlands. Fifteen pages.

In 2024, five annexes. Anexo H showed up, declaring health and education expenses. Eighteen pages.

My situation didn't change between these years. Same activity. Same NHR status. Same family. But every year the filing got bigger and covered more ground. Understanding why took reading all three declarations together.

The variation isn't a signal something went wrong. Different accountants approach the same situation differently, and the same accountant's approach can shift between years as rules change or as a client's profile comes into sharper focus. That's normal. What wasn't normal was me not understanding any of it.

The part actually worth understanding: the 15% proof

The simplified regime's 15% expense proof is the piece I wish someone had explained to me in year one. Here's the mechanism.

Portugal's simplified regime assumes 25% of your gross income goes to professional expenses. You don't have to prove those 25%. But you do have to prove at least 15% in documented professional expenses. If you can't, the shortfall is added directly to your taxable income.

Social Security contributions count toward that 15%. Mine were about 14,500 euros in 2024. They appear in Quadro 17 of Anexo B.

Looking at my 2022 and 2023 filings, I noticed the Social Security contributions weren't there. When I finally dug into it, I understood why this matters even if the headline number doesn't change much: if your documented expenses consistently fall short of 15%, the difference compounds into your taxable base year after year. Under NHR with the 20% flat rate, the impact was smaller than it would be under progressive rates. But the mechanism is the same.

If you're on the simplified regime, Quadro 17 is the section that answers: which of your expenses were classified as professional, which counted toward the 15%, and why. That's worth reading.

The same muscle you use to understand the 15% proof is the one you need for keeping the documents that back it up. Which expenses actually qualified? Do you have the invoices? Knowing what counted is inseparable from keeping the records that prove it. (The retention rules in Portugal are worth understanding for exactly this reason.)

The dependent that wasn't there

My daughter is in every declaration for 2022 and 2023. Her NIF is right there in Quadro 6B. In 2024, she's missing.

She's still living with us. She's still under age. Something was left out between years.

If something looks different from what you'd expect, there's usually a good reason. Under NHR with the 20% flat rate, having a dependent might not change the final tax amount for a given year. It still changes the quociente familiar calculation, and it's worth understanding the interaction. Maybe it mattered, maybe it didn't. My accountant may have had a reason I wasn't aware of. But I was never in a position to know, because I'd never read that part of the filing.

On progressive rates, a missing dependent is a clear cost. Under NHR, the impact depends on how the autonomous taxation interacts with the household calculation. Either way, it's the kind of thing that only becomes visible when you read the filing yourself.

The expense strategy across years

Quadro 17C of Anexo B lets you manually declare business expenses instead of relying on what the AT has on file from e-fatura. In 2022, my accountant opted in and declared 1,564 euros. In 2023, they didn't opt in at all. In 2024, they opted in again with 1,915 euros.

Same kind of expenses. Three different approaches.

I don't know which approach was optimal in each year. Different accountants file differently, and the same accountant may shift approach as the picture becomes clearer or as rules change. That's valid professional judgment. But it's also something a client should understand: whether manually declaring expenses in Quadro 17C is right for your situation, and what the implications are either way. That's the question I now know to ask.

The annex that might do nothing

The biggest addition in 2024 was Anexo H, declaring health expenses (3,720 euros) and education expenses (94 euros). It looks thorough. It's also possibly redundant in my specific situation.

Under NHR, my Category B income is taxed at a flat 20% through autonomous taxation. Personal deductions like health and education reduce the coleta calculated on the progressive tax scale. But I'm not on the progressive scale. My income goes through the 20% flat rate in Anexo L.

If I'm right about this, the annex had no effect on what I owe. I'm genuinely not certain. The interaction between NHR autonomous taxation and personal deductions is one of those areas where even specialists can disagree. My accountant may have added it to be thorough, or because the rules are ambiguous enough that including it is the safer call. Both are defensible. But it's a question I now want to understand for myself.

Foreign income appeared halfway through

I have a Swedish bank account. It earns small amounts of interest and dividends. In 2022, this wasn't declared at all. In 2023, Anexo J appeared with entries from Sweden and the Netherlands. In 2024, just Sweden.

Did I have foreign income in 2022? Yes. The same account existed. Should it have been declared? Under NHR with the exemption method for foreign income, the tax effect might be zero. But the reporting obligation exists regardless. Whether this was a gap or a judgment call, I can't tell. I never got an explanation.

The visibility gap

I never got a breakdown of what was sorted out each year, or why. That's what I mean by a visibility gap, and I want to be clear it's not a criticism of my accountant specifically. She manages dozens of clients during filing season. The filings are dense, the forms are in Portuguese, the rules shift annually, and the AT portal gives no tools to compare across years.

The honest part is this: because I couldn't see what was filed or why, I can't even tell whether anything actually cost me. Maybe those SS contributions would have made no difference to my final number. Maybe the missing dependent was immaterial under NHR. I was never in a position to know either way. And you can't make sure nothing's left on the table if you never see the table.

That's not a workflow that works for anyone. The accountant works with what they're handed. The client signs off on something they can't read. Both are doing their best within a system that makes verification hard. Closing that loop is something both sides benefit from.

What I want to exist

I want to upload my declaration and see it explained clearly. What was filed? What does each section mean? What changed from last year?

For the cases where nothing actually changed, the output should be simple: "Your situation is the same as last year. Here's the pre-filled declaration. Review it, and upload the XML to the AT portal."

For the cases where something looks different, it should surface the question: "Your Social Security contributions are in Quadro 17 this year but not the prior two. Here's what that means for your 15% expense calculation."

That's the version I'm building at Descodify. Not to replace accountants. They understand Portuguese tax law in ways I never will. But to give both sides better tools. The freelancer finally understands what's been filed. The accountant has a system that catches the gaps an 80-client workload makes invisible.

For the 15% expense proof specifically, what changes is that you can see exactly which expenses were counted, whether you hit the threshold, and what was left undeclared. That means you can have an informed conversation with your accountant instead of signing off on something you've never seen.

Related: I gave my tax portal password to my accountant: the story of how I ended up doing my own administration.