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RELATED-PARTY TRANSACTIONS - Guarantees granted (Details) - Joint-venture - Financial guarantees - BRL (R$) R$ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Gerdau Corsa S.A.P.I de C.V. |  |  |
Guarantees granted |  |  |
Original Amount | R$ 1,750,249 |  |
Carrying Amount | 2,242,865 | R$ 1,784,868 | R$ 1,933,929
Gerdau Summit Acos Fundidos e Forjados S.A. |  |  |
Guarantees granted |  |  |
Original Amount | 130,164 |  |
Carrying Amount | 30,125 | 37,285 | 41,571
Gerdau Metaldom S.A; Aceros Corsa S.A De C.V |  |  |
Guarantees granted |  |  |
Original Amount | R$ 274,560 |  |
Carrying Amount |  | R$ 241,842 | R$ 198,619

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