With some constitutional amendments, most notably the 1979 constitutional amendment, Article XV, Section 1, California's usury limit is now generally 10% per year with a broader range of exemptions.
A credit line deed of trust shall set forth on the front page, either in capital letters or in language underscored, the words "THIS IS A CREDIT LINE DEED OF TRUST." Such phrase shall convey notice to all parties that advances or other extensions of credit are to be made or are contemplated to be made from time to time ...
There is no federally mandated maximum interest rate for credit cards. For credit cards, the CARD Act offers various protections and provides more transparency when it comes to rates.