Clarification on Minimum Balance / Gas Buffer for SOL Withdrawals

Support
1

Hi Team,

I’m trying to withdraw SOL from a Fireblocks vault using the Fireblocks Web3 SDK. The issue is consistent: whenever I attempt to withdraw the entire balance minus the estimated network fee, the transaction fails with an “Insufficient Funds” error.

After digging into this, it appears Fireblocks enforces a non-withdrawable buffer balance that must remain in the account, regardless of the estimated fee. However, I haven’t been able to find any clear documentation specifying:

  1. The exact minimum SOL balance that must be retained

  2. Whether this buffer is static or dynamic

  3. Whether it applies at the vault, asset, or transaction level

Could you please confirm the exact required buffer amount for SOL withdrawals?

Additionally, I’d like to know if the same buffer logic applies to UTXO-based chains such as BTC, DOGE, and Litecoin, or if their withdrawal mechanics differ (e.g., dust limits, fee estimation behaviour, or Fireblocks-specific constraints), because I faced similar issues in these chains.

Clear numbers or references to official documentation would really help here.

Thanks in advance.