v3.25.4
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Tax contingencies (Details) - BRL (R$)
R$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
Gerdau Acos Longos S.A. and Gerdau Acominas S.A. | Goodwill Deductibility | Voluntary Appeal, Filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities R$ 4,971,219 R$ 4,721,327
Gerdau Acominas S.A., Gerdau Acos Longos S.A., and Gerdau Acos Especiais S.A. | Goodwill Deductibility | Administrative collection    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 8,545,810 8,154,991
Gerdau Acos Longos S.A. | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 689,134 637,367
Gerdau Acos Longos S.A. | Goodwill Deductibility | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 775,120 719,697
Gerdau Acos Longos S.A. | Goodwill Deductibility | Awaiting judgement, lower court    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 6,636 6,257
Gerdau Acos Longos S.A. | Goodwill Deductibility | Awaiting Judgement, Embargoes to Tax Enforcement    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 741 101,719
Gerdau Acos Longos S.A. | Goodwill Deductibility | Superior Chamber of Tax Appeals    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 286,671 266,020
Gerdau Acos Longos S.A. | Goodwill Deductibility | Embargo to Enforcement, Filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 528,071 493,284
Gerdau Acos Longos S.A. | Goodwill Deductibility | Motion for clarification filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 383,502 360,286
Gerdau Acos Longos S.A. | Goodwill Deductibility | Notice of judgment received    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 408,042 384,696
Gerdau Acos Longos S.A. | Goodwill Deductibility | Voluntary Appeal, Filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 190,252 177,719
Gerdau Acos Especiais S.A. | Goodwill Deductibility | Special Appeal, Filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 176,793 164,503
Gerdau Acos Especiais S.A. | Goodwill Deductibility | Special appeal, pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 129,629 122,116
Tax contingencies | IPI credit on inputs | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 571,299 501,588
Tax contingencies | Non-approval of compensation of credits on inputs | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 2,126,191 2,137,038
Tax contingencies | Social security contributions | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 172,301 159,220
Tax contingencies | Other Taxes | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 854,422 772,337
Tax contingencies | Goodwill Deductibility | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 628,534 582,795
Tax contingencies | Goodwill Deductibility | Special Appeal, Filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 34,406 31,818
Tax contingencies | Goodwill Deductibility | Voluntary Appeal, Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 289,734 269,586
Tax contingencies | Goodwill Deductibility | Voluntary Appeal, Lodged Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 209,453 193,162
Tax contingencies | Goodwill Deductibility | Voluntary Appeal, Filed    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 94,941 88,229
Tax contingencies | Gerdau Acos Longos S.A. and Gerdau Acominas S.A. | ICMS (State Value Added Tax) | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 999,844 625,877
Tax contingencies | Gerdau Acos Longos S.A. | Withholding Income Tax    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 1,643,601 1,708,269
Tax contingencies | Gerdau Acos Longos S.A. | Withholding Income Tax | Administrative processing    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 759,834 880,730
Tax contingencies | Gerdau Acos Longos S.A. | Withholding Income Tax | Superior Chamber of Tax Appeals    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 883,767 827,539
Tax contingencies | Gerdau Internacional Empreendimentos Ltda. and Gerdau Acos Especiais S.A | IRPJ - Corporate Income Tax and CSLL - Social Contribution Tax | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 1,568,352 1,486,615
Tax contingencies | Gerdau Internacional Empreendimentos Ltda | Corporate Income Tax and Social Contribution Tax | Pending    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 1,289,971 1,222,634
Tax contingencies | Gerdau Internacional Empreendimentos Ltda. - Grupo Gerdau | IRPJ - Corporate Income Tax and CSLL - Social Contribution Tax | Administrative processing    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities 2,550,462  
Tax contingencies | Gerdau Acos Especiais S.A. | Corporate Income Tax and Social Contribution Tax | First instance, awaiting judgement of the Tax Enforcement Embargoes    
TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS    
Estimated financial effect of contingent liabilities R$ 278,381 R$ 263,981