Vault Locks and Unlocks are free of charge.
The only fee associated with the Vault is the annual custodial fee, which is calculated daily and charged upon unlocking.
The current fee can be found listed here.
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Please note: Vault Unlocks resulting from external deposits (e.g., user-initiated bitcoin transfers from third-party wallets to a Bitaroo Vault address) will incur a mining fee, which is entirely passed on to the miners.