Cal. Gov't Code § 95020.5

(a) Effective July 1, 2011, regional centers shall begin transitioning providers of early intervention services purchased through a regional center to electronic billing. All providers of early intervention services provided or purchased through a regional center shall submit all billings electronically for services provided on or after July 1, 2012, with the exception of the following:
1. (1) A provider whose services are paid for by vouchers, as that term is defined in subdivision (i) of Section 4512 of the Welfare and Institutions Code.
2. (2) A provider who demonstrates that submitting billings electronically for services presents a substantial financial hardship.
(b) For purposes of this section, “electronic billing” is defined as the Regional Center e-Billing System web application provided by the State Department of Developmental Services.