Filing a tax return according to the form 3-NDFL — a mandatory procedure for individuals who received income outside their main place of work or who claim tax deductions. In 2026, the Federal Tax Service of Russia simplified the process: now you can fill out and send the declaration completely online via Taxpayer personal account (LKN) or service Tax.ru. But even with digitalization, many encounter errors during registration - from incorrectly indicating income codes to missing required fields.
This article will help you figure out how correctly fill out 3-NDFL online in 15-20 minutes, avoiding common mistakes. We will look at a step-by-step algorithm for different situations: receiving a deduction for treatment, selling property, dividends or renting out an apartment. We will also explain what documents will be required, how to correct errors after sending, and what to do if the tax office requests clarification.
Since 2023, changes have been made to form 3-NDFL: new deduction codes have been added (for example, 328 for investment deductions under IIS), the procedure for confirming income from cryptocurrency transactions has been simplified, and the time frame for desk audits has been reduced to 2 months (previously - 3). It is important to take these novelties into account when filling out the declaration for 2023 (due in 2026).
Who must submit 3-NDFL in 2026
Individuals are required to submit a declaration in form 3-NDFL in the following cases:
- 💰 Received income from something other than your main place of work: from renting out real estate, selling a car/apartment, freelancing, dividends or winnings.
- 🏥 Claim tax deductions: social (treatment, education), property (purchase of housing), investment (individual investment system, securities).
- 🌍 Have income from abroad: salary from a foreign employer, income from foreign investments.
- 💎 The property was sold for less than the cadastral value (for example, an apartment for 1 million rubles with a cadastral price of 3 million rubles).
If you just get paid at the main place of work (under an employment contract), there is no need to submit 3-personal income tax - the tax agent (employer) withholds and transfers personal income tax himself.
In 2026, a return for 2023 must be filed by everyone who received income from the sale of property owned for less than 3 years (for real estate) or 1 year (for transport). An exception is if the sale price did not exceed 1 million rubles for real estate or 250 thousand rubles for other property.
Deadlines for filing 3-NDFL in 2026
The deadline for submitting the declaration is April 30, 2026 for income received in 2023. This rule applies to everyone who is required to report income (sale of property, rent, freelancing, etc.). For those who claim only deductions (for example, for treatment or the purchase of housing), there are no deadlines - the declaration can be submitted at any time within 3 years.
Important: if April 30 falls on a weekend, the deadline is automatically transferred to the next working day. In 2026 it is Monday, May 6 (April 30 is Tuesday, but not a day off).
| Situation | Deadline for filing 3-NDFL | Tax payment deadline |
|---|---|---|
| Income from the sale of property, rent, freelancing | Before April 30, 2026 | Before July 15, 2026 |
| Tax deductions (treatment, education, purchase of housing) | Any time (but no later than 3 years from the date of expenses) | — |
| Dividends from Russian companies | Until April 30 (if the tax is not withheld by the agent) | Until July 15 |
| Income from cryptocurrencies (if exceeded 600 thousand rubles per year) | Until April 30 | Until July 15 |
⚠️ Attention: If you missed the deadline for filing a declaration, the Federal Tax Service may impose a fine - 5% of the unpaid tax amount for each month of delay (minimum 1,000 ₽). In case of deliberate evasion, the fine increases to 40% of the tax amount.
Step-by-step instructions: how to fill out 3-NDFL online
The most convenient way is through Taxpayer personal account on the website Tax.ru. To do this, you will need a verified account (login/password from State Services or a qualified electronic signature).
Algorithm of actions:
- Log in in LKN through State Services or by login/password from the tax office.
- Go to section
Life situations → Submit a 3-NDFL declaration. - Select year (2023) and declaration type:
- 📄 "Declaration" - if you are reporting income.
- 💸 "Application for deduction" — if you are applying for a tax refund.
☑️ What to check before sending 3-NDFL
If you are filling out a declaration for the first time, the system will offer a step-by-step assistant. A mode is available for advanced users "Expert" - it allows you to manually edit all fields, including rare income codes (for example, 1530 for income from cryptocurrencies).
Section "Income": how to fill it out correctly
This is the most important block of the declaration. Errors here lead to denial of deductions or additional taxes. Basic rules:
- 📌 Revenue codes are taken from Federal Tax Service directory. For example:
1520— income from the sale of real estate;1400— rent;1010— dividends.
- 💵 Amounts of income indicate no kopecks (round according to the rules of mathematics).
- 📅 Date of receipt of income - this is not the day of money transfer, but the day actual receipt (for example, for rent - the last day of the month for which they pay).
Example of filling out for selling a car:
Section "Income":
- Source of payment: Full name of the buyer (or “Individual”)
- Revenue code: 1512 (sale of vehicles)
- Amount of income: 850,000 (if the car is sold for 850 thousand ₽)
- Date: 06/15/2023 (date of signing the purchase and sale agreement)
⚠️ Attention: If you sold the property cheaper than 70% of the cadastral value (for real estate) or market (for transport), the tax office may charge additional personal income tax on the difference. For example, if you sold an apartment for 2 million rubles with a cadastral value of 3 million rubles, the tax will be calculated on 2.1 million rubles (70% of 3 million).
If you don’t know the income code, use a search in the Federal Tax Service directory using a keyword (for example, “rent” or “dividends”). The system will prompt you with current codes for 2026.
Section "Deductions": how to indicate and confirm
Deductions reduce the tax base or allow you to return part of the personal income tax paid. In 2026, the following types are in effect:
| Type of deduction | Maximum amount | Deduction code | Documents for confirmation |
|---|---|---|---|
| Property (purchase of housing) | 260 thousand ₽ (up to 2 million ₽ expenses) | 311 | Purchase and sale agreement, transfer and acceptance certificate, payment invoices |
| Social (treatment) | 120 thousand ₽ (including training) | 321 | Agreement with the clinic, checks, license of the medical institution |
| Investment (IIS type A) | 52 thousand ₽ (13% of 400 thousand ₽) | 328 | Extract from the broker, agreement for maintaining IIS |
| Professional (freelancers) | No restrictions (but no more than actual costs) | 403 | Agreements, acts, checks for equipment |
To indicate a deduction on your return:
- In the section
"Deductions"select the appropriate type (for example, "Social"). - Specify deduction code (see table above).
- Enter amount of expenses (for example, 150 thousand rubles for treatment).
- Attach scans of documents (checks, contracts) in PDF or JPG format.
Important: If you are claiming a deduction for several years (for example, for treatment in 2022 and 2023), you need to submit separate declaration for each year.
How to return tax for a child's education?
To do this, indicate the deduction code in the declaration 325 (social deduction for children's education). You will need:
- Agreement with an educational institution (in the name of the child);
- License of an educational organization;
- Payment documents (checks, receipts).
The maximum deduction amount is 50 thousand rubles for each child per year (13% return - 6.5 thousand rubles).
Typical mistakes when filling out 3-NDFL and how to avoid them
According to the Federal Tax Service, 30% declarations contain errors due to which the tax office suspends the audit or refuses deductions. The most common mistakes:
- 🔢 Incorrect income/deduction codes - for example, an indication
1400(rent) instead1520(real estate sales). - 📅 Errors in dates — indicating the date of transfer of money instead of the date of receipt of income.
- 💰 Unaccounted income — forgot to indicate interest on the deposit or a gift over 4 thousand ₽.
- 📄 Lack of supporting documents - for example, they did not attach the purchase and sale agreement to the deduction for housing.
- 🔄 Resubmitting a return without recalling the previous one (the system can only count the first one).
How to check the declaration before sending:
- Use built-in validator in LKN - it will highlight critical errors.
- Check income amounts with 2-NDFL certificates (if any).
- Check that all fields are filled in — empty cells can cause refusal.
If the tax office discovers an error, it will send a notification to LKN with a requirement to correct the declaration within 5 days. Ignoring will result in suspension of the scan.
Example of a typical error:
❌ Situation: A citizen sold an apartment for 2.5 million rubles, but indicated an income of 1 million rubles in the declaration (to reduce tax).
✅ Consequences: The tax office will compare the data with Rosreestr and charge additional personal income tax on the real amount (2.5 million rubles), plus a 20% fine for underestimating the tax base.
What to do after submitting the declaration
After successfully sending 3-NDFL to LKN, a notification with a registration number will appear. Next steps:
- Track status in section
"My taxes → 3-NDFL". Statuses:- 🔄 "Under Check" — declaration in progress (up to 2 months).
- ✅ "Accepted" - the verification has been passed, you can apply for a deduction.
- ❌ "Needs clarification" - errors need to be corrected.
Tax refund deadline for deduction:
- 🕒 1 month - to check the application;
- 🕒 1 month — for transferring money (total up to 2 months).
⚠️ Attention: If the tax office requests additional documents (for example, original checks), send them via LKN within 10 days. Otherwise, the deduction will be denied.
FAQ: Answers to frequently asked questions
Can I fill out 3-NDFL on paper and take it to the tax office?
Yes, but it's less convenient. The declaration form can be downloaded from the Federal Tax Service website, printed, filled out by hand and submitted to any Federal Tax Service Inspectorate (regardless of registration). However verification of a paper declaration takes up to 3 months (versus 2 months for electronic). In addition, you will have to stand in line.
Do I need to file 3-NDFL if I sold a car for 150 thousand rubles?
No, if the car was owned more than 1 year and the selling price does not exceed 250 thousand rubles. In this case, income is exempt from taxation (clause 17.1 of Article 217 of the Tax Code of the Russian Federation). If you own the car less than a year, a declaration must be filed, but you will not have to pay tax (a deduction of 250 thousand rubles will cover the amount of the sale).
How can I correct an error in a return that has already been submitted?
Need to submit updated declaration:
- Log in to LKN, find your declaration in the section
"My taxes". - Click
"Submit an updated declaration". - Correct any errors and resubmit.
If the error resulted in understatement of tax, you will have to pay an additional amount + penalties (0.08% for each day of delay).
Can I get a deduction for treatment if I paid in cash?
Yes, but you need to confirm the expenses. To do this:
- Pick it up at the clinic cash payment certificate (indicating your full name, amount and type of service).
- Attach it to the declaration along with the receipt (if preserved) and the contract.
The Federal Tax Service may request original documents for verification.
What happens if you don’t file 3-NDFL when selling an apartment?
If you were required to submit a declaration (for example, you sold an apartment for less than 70% of the cadastral value), but did not do so, the consequences are as follows:
- 📛 Fine — 5% of the unpaid tax for each month of delay (minimum 1,000 ₽).
- 🔍 Additional tax assessment — The Federal Tax Service itself will calculate the personal income tax according to Rosreestr data and send a request for payment.
- ⚖️ Account blocking — if you don’t pay your tax on time, the tax office may seize your bank accounts.
We recommend filing a declaration even late - so the fine will be minimal.