Is it okay to lend my own money to my startup, and how do I do it cleanly?

Founders do this often, and it is fine as long as you make it a documented transaction rather than a blur. Decide whether the money is going in as a loan or as capital, because they sit differently on your cap table and are treated differently in tax and accounting. If it is a loan, put it in writing with the amount, any interest, and repayment terms, and move it through the company bank account so there is a clear trail. Avoid the pattern of quietly covering random company bills from your personal card and never recording it, which muddies both sets of books. Keep proof of what went in, so if you draw it back later it reads as repayment, not income. Rules on founder loans, interest, and their tax treatment change and depend on your company type, so confirm the clean structure with a CA before you rely on it.