You have been trading crypto for years and never declared any of it. You assumed that as long as you did not move the money to your bank, the tax agency would never find out. Or you simply did not know that every swap, every sale and every staking reward creates a tax liability.
Now you know. And you want to fix it before a letter turns up.
The good news: you can put your position right by filing amended returns. And there is an advantage few people are aware of: the work involved in calculating this year’s FIFO correctly already covers every earlier year.
If you are still unsure whether your case calls for an amended return, start with this guide: I never declared my crypto, what to do with the tax agency.
What is an amended return?
An amended return corrects an income tax return you have already filed. It is used when:
- You forgot to include income or gains
- You made mistakes that shortchanged the tax agency (you paid too little)
- You want to come forward voluntarily before you get caught
Important: an amended return adds to what you already declared. It does not replace the original return; it corrects it by adding what was missing.
Two very common situations
At colvence we see these cases constantly:
1. “The tax agency had not spotted my transactions… until now”
You traded for years on Binance, KuCoin or exchanges with no Spanish presence. You did not declare because you thought you were off the radar.
Now the CRI001 notice shows up in your draft return, or you can simply see that DAC8 comes into force in 2026 and you would rather get ahead of it.
2. “I did not know I had to declare”
You thought you only had to declare if you cashed out euros to your bank. Or that crypto-to-crypto swaps were not taxed. Or that staking “did not count” until you sold.
Now you understand that every transaction is a taxable event and you want to bring everything up to date retroactively.
The problem: calculating FIFO requires your whole history
Here is the key point many people miss:
To work out correctly what you owe on your 2025 return, you need to know the price you paid for each coin. And if you bought BTC in 2020, 2021, 2022… the FIFO method requires you to sell the oldest units first.
Without the complete history there is no correct FIFO. And without a correct FIFO, your return is wrong.
That means if you come to colvence for your 2025 report, we already have to rebuild 2020, 2021, 2022, 2023 and 2024 for the numbers to add up.
The work is already done. All that is left is deciding whether or not you file the amended returns.
The opportunity: putting everything right in one go
Our process is straightforward:
| Step | What we do |
|---|---|
| 1. Collection | We extract the complete history from every one of your exchanges and wallets |
| 2. Consolidation | We merge everything into a single timeline |
| 3. FIFO calculation | We apply the FIFO method year by year, from the very beginning |
| 4. Annual reports | We produce the P&L for each tax year |
| 5. Amended returns | We prepare the returns for whichever years you need to put right |
| 6. Filing | Our tax specialist coordinates the filing with the tax agency |
The result: you sleep soundly knowing everything is in order.
How many years can I put right?
The tax agency can review the last four years (five where there is a tax offence). That means that in 2026 they can look at:
| Tax year | Can they review it? |
|---|---|
| 2025 | Yes |
| 2024 | Yes |
| 2023 | Yes |
| 2022 | Yes |
| 2021 | Time-barred (except for offences) |
Tip: even though 2021 is time-barred, we need that history to calculate FIFO correctly. Purchases made in 2021 affect sales made in 2025.
Surcharges for filing late (voluntarily)
If you file the amended return before the tax agency makes a formal demand, you pay a surcharge but avoid the penalty:
| Delay after the deadline | Surcharge |
|---|---|
| Up to 3 months | 5% |
| 3 to 6 months | 10% |
| 6 to 12 months | 15% |
| More than 12 months | 20% + interest |
Compare that with the penalties for failing to declare: from 50% to 150% of the tax due. The difference is enormous.
A worked example:
- Tax not declared in 2023: €3,000
- If you come forward voluntarily (>12 months): €3,000 + €600 (20% surcharge) = €3,600
- If the tax agency catches you (serious penalty): €3,000 + €2,250 (75% average penalty) = €5,250
You save €1,650 by doing it voluntarily. And you avoid the stress of an inspection.
What about the Modelo 721?
If you held more than €50,000 on foreign exchanges on 31 December in any year and did not file the Modelo 721, you can put that right too.
A Modelo 721 filed late but voluntarily carries a fixed penalty of €300 (where there has been no prior formal demand). That is far better than the €5,000 per item of data that applies if you get caught.
Frequently asked questions
What if I made losses in earlier years?
Even better. Capital losses can be offset against gains over the following four years. If you lost money in 2022 and made a gain in 2025, you can reduce what you pay in 2025.
Putting your position right lets you take advantage of those losses you never declared.
Does your specialist file everything?
Yes. The full service covers:
- P&L reports for every year
- Preparation of the amended returns
- Filing with the tax agency
All you have to do is upload the files and sign off on the numbers.
Summary
| Item | Detail |
|---|---|
| What it is | Correction of returns for earlier years |
| When to do it | Before the tax agency makes a formal demand |
| Advantage | Surcharge (5–20%) instead of a penalty (50–150%) |
| Years open to review | The last four tax years |
| Why do it with us | FIFO already requires the complete history |
Want to put your position right?
At colvence we do the whole job: from extracting your history to filing the amended returns. Since we need to rebuild everything anyway to calculate FIFO correctly, we take the chance to leave it all in order.
Better to sleep soundly than to wait for the letter.
Víctor Lázaro
Tax adviser, colvence.com
