In Bitrefill's
TOS, they’ve got a paragraph that states that:
The sale of Bitrefill Balance Cards and Bitrefill Balance credit is subject to the limitations provided in these Terms Bitrefill reserves the right to, at any time <…>
(v) require a Customer to undertake KYC in order to continue to use any of the Bitrefill Balances and (vi) freeze access to the account or to the Bitrefill Balance while investigating suspicious activity.
It seems that they can therefore ask for KYC at any moment in time. Not sure what may trigger the requirement (some algorithm that analyses this and that I figure), nor how frequently it happens to date, but the KYC procedure, once triggered, asks for IdCard, selfie, proof of residence and a financial background questionnaire. All in all, exceedingly intrusive and not something you’d want waiting to be leaked.
See also:
https://cryptogazette.com/the-fall-of-bitrefill-kyc-requirements-take-out-another-crypto-firm/According to their TOS, you can still get away without creating an account with 500$ per day and 1K $ per month limits for orders, and tenfold those figures with a basic account that only required an email. Verified accounts (I figure with some sort of voluntary KYC) increase the range further.