v3.26.1
BASIS OF CONSOLIDATION AND INVESTMENTS (Details)
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
C S N Islands V I I Corp [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Financial transactions  
C S N Inova Ventures [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Equity interests and financial transactions  
C S N Islands X I I Corp [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Financial transactions  
C S N Steel S L U [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Equity interests and financial transactions  
Td B B S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business  Equity interests  
Sepetiba Tecon S. A. [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Port services  
Minerios Nacional S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Mining and Equity interests  
Companhia Florestaldo Brasil [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Reforestation  
Estanho De Rondonia S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Tin Mining  
Companhia Metalurgica Prada [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.89% 99.89%
Core business Manufacture of containers and distribution of steel products  
C S N Mineracao S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 69.01% 69.01%
Core business Mining  
C S N Energia S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Sale of electric power  
F T L Ferrovia Transnordestina Logistica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 92.71% 92.71%
Core business Railroad logistics  
Nordeste Logistica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Port services  
C S N Inova Ltd [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Advisory and implementation of new development project  
C B S I Companhia Brasileira De Servicos De Infraestrutura [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Equity interests and product sales and iron ore  
C S N Cimentos Brasil S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Cement manufacturing  
Berkeley Participacoes E Empreendimentos S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Electric power generation and equity interests  
C S N Inova Solucoes S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Equity interests  
C S N Participacoes I S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.90% 99.90%
Core business Equity interests  
C S N Participacoes I I I S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.90% 99.90%
Core business  Equity interests  
C S N Participacoes I V S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.90% 99.90%
Core business Equity interests  
C S N Participacoes V S. A. [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.90% 99.90%
Core business  Equity interests  
C S N Incorporacao E Participacoes Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Equity interests  
Estrela Comercioe Participacoes S. A. [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Equity interests  
Circula Mais Servicos De Intermediacao Comercial S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 0.10% 0.10%
Core business Commercial intermediation for the purchase and sale of assets and materials in general  
Lusosider Projectos Siderurgicos S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Equity interests and product sales  
Lusosider Acos Planos S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Steel and Equity interests  
C S N Resources S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Financial transactions and Equity interests  
Companhia Brasileira De Latas [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.89% 99.89%
Core business Sale of cans and containers in general and Equity interests  
Companhia De Embalagens Metalicas M M S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.88% 99.88%
Core business Production and sale of cans and related activities  
Companhia De Embalagens Metalicas M T M [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.88% 99.88%
Core business Production and sale of cans and related activities  
C S N Productos Siderurgicos S L [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Financial transactions, product sales and Equity interests  
Stalhwerk Thuringen Gmb H [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Production and sale of long steel and related activities  
C S N Steel Sections Polska Sp Zoo [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Financial transactions, product sales and Equity interests  
C S N Mining Holding S L U [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 69.01% 69.01%
Core business Financial transactions, product sales and Equity interests  
C S N Mining Gmb H [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 69.01% 69.01%
Core business Financial transactions, product sales and Equity interests  
C S N Mining Asia Limited [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 69.01% 69.01%
Core business Commercial representation  
Lusosider Iberica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Steel, commercial and industrial activities and equity interests  
Companhia Siderurgica Nacional L L C [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Import and distribution/resale of products  
Elizabeth Cimentos S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Cement manufacturing  
Santa Ana Energetica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Electric power generation  
Topazio Energetica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Electric power generation  
Brasil Central Energia Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Electric power generation  
Circula Mais Servico De Intermediacao Comercial S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.90% 99.90%
Core business Commercial intermediation for the purchase and sale of assets and materials in general  
Metalgrafica Iguacu S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.89% 99.89%
Core business  Metal packaging manufacturing  
Companhia Energetica Chapeco [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 69.01% 69.01%
Core business Electric power generation  
Companhia Estadual De Geracaode Energia Eletrica C E E E G [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Electric power generation  
Ventosde Vera Cruz S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Electric power generation  
Ventosde Curupira S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business  Electric power generation  
Ventosde Povo Novo S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 99.99%
Core business Electric power generation  
M A Z E T Maschinenbau Zerspanungstechnik Unterwellwnborn Gmb H [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business  Production and sale of long steel and related activities  
C S N I T C Solutions A G [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 55.21%  
Core business  Financial transactions, product sales and Equity interests  
C S N Mining Internacional Gmb H [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 69.01% 69.01%
Core business Commercial and representation of products  
Gramperfil S. A. [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 90.00%  
Core business Manufacturing and sale of metal profile  
C S N International Steel Gmb H [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Commercial and representation of products  
Tora Transportes Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Road transport  
Tora Locacoes S. A. [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Road transport and automobile rental  
F J X Transportes S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 42.00%  
Core business  Road transport and logistic  
N. Minas Transportese Locacoes Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business  Road transport and logistic  
Saratoga Transportes Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Road transport  
Lokamig Renta Car S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Automobile rental  
Seminovos Lokamig Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Automobile rental  
Tora Logistica Armazense Terminais Multimodais S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Logistics  
Tora Recintos Alfandegarios S. A. [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business General storage operations and road transport  
Tora Seminovos Comerciode Veiculos Ltda [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 70.00%  
Core business Commercial and automobile rental  
C S N Captive Insurance Company L L C [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00%  
Core business Captive Insurance Company  
Global Dot Com S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 80.00%  
Core business Information service provision  
Galvacolor Jerez S. L. U [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00%  
Core business Transformation and commercialization of steel products  
Ita Energetica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 48.75% 48.75%
Core business Electric power generation  
M R S Logistica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 7.59% 18.75%
Core business  Railroad transportation   
Aceros Del Orinoco S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 31.82% 31.82%
Core business Dormant  
Transnordestina Logistica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 33.89% 48.03%
Core business  Railroad logistics   
Equimac S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 50.00% 50.00%
Core business  Rental of commercial and industrial machinery and equipment   
M R S Logistica S A 1 [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 20.64% 12.93%
Core business  Railroad transportation   
Arvedi Metalfer Do Brasil S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 20.00% 20.00%
Core business  Metallurgy and Equity interests   
Panatlantica S. A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 29.92% 29.92%
Core business Steel  
Jaguari Energetica S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 10.50% 10.50%
Core business Electric power generation  
Chapecoense Geracao S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 9.00% 9.00%
Core business Electric power generation  
Companhia Energetica Riodas Antas Ceran [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 30.00% 30.00%
Core business Electric power generation  
Foz Chapeco Energia S A [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 9.00% 9.00%
Core business Electric power generation  
Diplic I I Private Credit Balanced Mutual Fund [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Investment fund  
Caixa Vertice Private Credit Balanced Mutual Fund [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Investment fund  
V R 1 Private Credit Balanced Mutual Fund [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 100.00% 100.00%
Core business Investment fund  
Consorcio Itauba [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 99.99% 100.00%
Core business Electric power generation  
Consorcio Passo Real [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 96.55% 100.00%
Core business Electric power generation  
Consorcio Da Usina Hidreletrica De Igarapava [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 17.92% 17.92%
Core business Electric power generation  
Consorcio Dona Francisca [Member]    
IfrsStatementLineItems [Line Items]    
Equity interests 15.00% 15.00%
Core business Electric power generation