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Form 2042-C — complementary income tax return

Form 2042-C is the complementary income tax return, an annex to the 2042, served on the same official page with the other annexes (2042-C-PRO for self-employed income, 2042-RICI for tax reductions and credits, 2042-IOM, 2042-TA). It carries what the main return does not: gains or losses on digital assets (boxes 3AN and 3BN, carried from form 2086, scale election 3CN), exempt salaries and pensions retained for the effective-rate computation (line 1AC), tax credits attached to foreign-source income (lines 8VL, 8VM, 8WM, 8UM) and, in its section 8 "Divers", affiliation to a social security scheme of another EEA State or Switzerland (boxes 8SH and 8SI). Online, its sections are selected at step 3; on paper, it is attached to the 2042.

Up to date for 2026 — verified on September 11, 2026Official form2042-CGuide: about 30 min

This content is part of the path: Filing my income tax return· Step 12 of 12· Last step of the path

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Deadlines

With the income tax return
The 2042-C follows the 2042 calendar: online, its sections are selected at step 3; on paper, it is attached to the main return sent to the individuals' tax office.

Documents to prepare

  • Completed annex 2086, for gains or losses on digital assets
  • Completed annex 2047, for foreign-source income and its taxation abroad
  • Amount of exempt salaries or pensions retained for the effective rate
  • Evidence of affiliation to a European or Swiss social security scheme, where applicable
Download the official form (2042-C)

You download it from the official site — we never re-host a public document.

What this page gives you

The guide above and the link to the official site. ActioFin does not produce any document for this page: whatever you fill in or file is done on the official medium.

Who this applies to

  • Individuals who made taxable disposals of digital assets during the year (carried from form 2086)
  • Employees, retirees or self-employed people receiving foreign-source income giving right to a tax credit, or exempt income retained for the effective rate
  • Taxpayers affiliated to the social security of another EEA State or Switzerland, not covered by a mandatory French scheme
  • Owners benefiting from a tax reduction reported on the 2042-C rather than on the 2044 (Malraux and historic-monument schemes after 2009)

Worked example

Example: Sonia, a freelance developer, combines a Swiss client and a cryptocurrency sale

Sonia runs a sole proprietorship in Lyon. In 2025 she made a €3,600 gain on privately held cryptocurrencies, and earned business income already reported on her 2042-C-PRO. In spring 2026, online, she selects at step 3 the sections of the complementary return: annex 2086 automatically fills box 3AN with €3,600; she does not tick box 3CN, the flat tax being more favourable than the scale. Her spouse, a cross-border employee affiliated to Swiss social security, ticks box 8SI of section 8 "Divers": his social levies depend on it. Without the 2042-C, neither the gain nor that affiliation would have been reported — and the 2042 alone would have been incomplete.

How to fill it in, step by step

  1. Identify what belongs to the 2042-C rather than to the 2042 or the other annexes: gains on digital assets (2086 → 3AN/3BN), exempt income for the effective rate (1AC), tax credits on foreign income (8VL, 8VM, 8WM, 8UM), affiliation to a European or Swiss social scheme (8SH, 8SI). Self-employed income goes on the 2042-C-PRO, common reductions and credits on the 2042-RICI.
  2. For foreign-source income, first fill in annex 2047: the gross income is carried to the 2042. Where the tax credit equals the FOREIGN tax, its AMOUNT is entered on the 2042-C, lines 8VL, 8VM, 8WM or 8UM. Where it equals the FRENCH tax, the 2042-C receives nothing: it is the TOTAL INCOME — not the credit — that is carried to line 8TK, 4BK or 4BL of the 2042.
  3. Exempt salaries or pensions retained for the effective-rate computation do not go on the 2047: they appear only on line 1AC and following of the 2042-C.
  4. For digital assets, fill in annex 2086: online, box 3AN or 3BN is filled automatically; on paper, carry the total yourself. Tick 3CN only if the progressive scale is more favourable — the election is final.
  5. If you are affiliated to the social security of an EEA State or Switzerland without a mandatory French scheme, tick 8SH (declarant 1) or 8SI (declarant 2) in section 8 "Divers".
  6. Online, select the sections at step 3 ("Sélection des rubriques de la déclaration de revenus et annexes"); on paper, download the 2042-C from the official page and attach it to the 2042, without using secure messaging.

The form, line by line

Boxes 3AN / 3BN / 3CN
Total gain or loss of the year on digital assets, from form 2086; 3CN for the election of the progressive scale, final and independent of the election for investment income.
Line 1AC
Exempt salaries or pensions retained for the effective-rate computation: they only appear on the 2042-C, never on annex 2047.
Lines 8VL, 8VM, 8WM, 8UM
Tax credit equal to the foreign tax, provided by the tax treaty, after reporting the gross income on the 2047 and carrying it to the 2042.
Boxes 8SH / 8SI (section 8 "Divers")
Affiliation to the social security of an EEA State or Switzerland, without a mandatory French scheme: the box tells the tax authority which social levies apply.

Good to know

  • Online filing is in principle mandatory; on paper, the official page recommends downloading the file before printing and sending it by post to the individuals' tax office, without using secure messaging.
  • The 2042-C does not carry self-employed income (2042-C-PRO) nor the most common tax reductions and credits (2042-RICI): three annexes, three purposes.
  • When the tax credit on foreign income equals the French tax, the 2042-C carries nothing: the TOTAL INCOME is reported on line 8TK, 4BK or 4BL of the 2042, never the amount of the credit.
  • The 2026 edition is the latest served by the official page, read on 11 September 2026; the 2042-C appears there alongside the 2042, 2042-IOM, 2042-C-PRO, 2042-RICI and 2042-TA.

Common mistakes

  • Reporting self-employed income on the 2042-C instead of the 2042-C-PRO, or a common tax reduction instead of the 2042-RICI.
  • Carrying exempt salaries retained for the effective rate to annex 2047: they go on line 1AC of the 2042-C.
  • Entering a tax-credit amount on line 8TK, 4BK or 4BL of the 2042: those lines receive the TOTAL INCOME. Only lines 8VL to 8UM of the 2042-C receive a credit amount, the one equal to the foreign tax.
  • Ticking 3CN by reflex: the scale election is final and only worthwhile if more favourable than the flat tax.
  • Forgetting 8SH or 8SI when affiliated to a Swiss or European social scheme — social levies depend on it.

Frequently asked questions

What is the difference between the 2042-C and the 2042-C-PRO?

The 2042-C is the complementary return for non-business income: gains on digital assets, exempt income for the effective rate, tax credits on foreign income, miscellaneous boxes. The 2042-C-PRO is the one for self-employed activities — micro-entrepreneurs, BIC, BNC, furnished rentals.

Where do I report my cryptocurrency gain?

On annex 2086, which details each disposal; online, it automatically fills box 3AN (gain) or 3BN (loss) of the return; on paper, you carry the total to box 3AN or 3BN of the 2042-C.

I have foreign income already taxed abroad: where does the tax credit go?

After reporting the gross income on annex 2047 and carrying it to the 2042: if the credit equals the foreign tax, enter its amount on lines 8VL, 8VM, 8WM or 8UM of the 2042-C; if it equals the French tax, carry the total income to line 8TK, 4BK or 4BL of the 2042 — that line does not receive the credit.

Go further

Compute the related amounts

Understand this form: the related course

Related forms

Official sources

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Guide and document provided for information purposes only; they do not constitute personalised legal or tax advice. Check the recipient organisation's requirements and consult a professional if needed.