Proof-of-ownership becomes necessary when the total value of a transfer exceeds €1,000 as per the Transfer of Funds Regulation. Note that individual transfers under €1,000 that exceed €1,000 cumulatively within a short timeframe are also affected. BISON will automatically prompt you for proof-of-ownership when required. After successful verification of your private wallet address, proof of ownership is only required again after 12 months.