Legal Question in Workers Comp in California

This is NOT a 'workers compensation' problem, this is a Breach of Contract problem. You will ultimately have to collect in Small Claims, which requires you make a demand for payment with an itemized billing...as this will be your 'evidence' for trial, this needs to crystal clear with dates payment is due and dates when late fees and interest begin to apply (giving the recipient of the work an easily-visible deadline by which the payment must be received by you).

EMAILING is a bad idea because there is no mechanism to prove to a small-claims volunteer judge the payor received the email. Snail Mail by USPS with Priority Mail, NO SIGNATURE REQUIRED, JUST plain old priority mail...that receipt is accepted by the court as evidence the defendant received the demand for payment will the bill (and a copy of the ads should be in that envelope, make it very very easy for the judge). When they still don't pay, you have to find the Agent for Service of Process for the magazine corporation, you cannot just deliver the Summons & Complaint to your former 'friends' at the magazine, you'll find the Agent at the California Secretary of STate webpage. And be ready: you can win in small claims and have a paper that the corporation owning the magazine owes you the money, then when the corporation goes bankrupt you get 5-cents for each dollar they owe you.