Iceland
Ordinary self-employment income taxed progressively up to ~46%, with the self-employed paying both employee and employer social/pension contributions. Crypto receipt is valued in ISK and taxed as income.
Self-employment / independent business activity income (Category B) - not capital gains.
Progressive 31.49-46.29% combined state + municipal (with presumptive remuneration rules for the self-employed).
Self-employed pays both shares; ~15.5% pension minimum plus ~6%+ social levies on calculated remuneration.
Register as sole proprietor (einstaklingsfyrirtaeki); pay monthly withholding on calculated remuneration; annual return to Skatturinn.
USDC is taxed as ordinary income at receipt (ISK value); later disposal gains taxable separately as capital income (~22%).