In conclusion: given all the above backend infrastructure and support for tax professionals and developers it appears that California indeed has e-file support, but they simply delegate the front end experience to third party software developers. There's no free general purpose application front end that's free online like Free File Fillable Forms. The state simply hasn't taken that on. And that begs the question. How exactly did the Federal government manage to originally get Intuit, and later On-LineTaxes, Inc. to build and maintain Free File Fillable Forms? Interestingly enough that new free file fillable forms provider has CA offerings https://www.olt.com/main/home/ca.asp

In conclusion: given all the above backend infrastructure and support for tax professionals and developers it appears that California indeed has e-file support, but they simply delegate the front end experience to third party software developers. There's no free general purpose application front end that's free online like Free File Fillable Forms. The state simply hasn't taken that on. And that begs the question. How exactly did the Federal government manage to originally get Intuit, and more recently On-LineTaxes, Inc. to build and maintain Free File Fillable Forms? Interestingly enough that new free file fillable forms provider has CA offerings https://www.olt.com/main/home/ca.asp

I'm not entirely sure how this works but there appears to be some mechanism for professional or high volume tax preparers to electronically transmit in the so called California e-file Program.

So there's definitely a backend that California has in place to receive an e-filed return, but there's no application front end that's just free online like Free File Fillable Forms.

So California undoubtedly has an e-file program, but it appears to be geared towards professional or high volume tax preparers to electronically transmit returns in their so called California e-file Program.

So there's definitely a backend that California has in place to receive an e-filed return, and they support at least all those form types enumerated above. CAFTB also posts documentation online about interfacing with software developers who write applications for the client half to publish returns back to CAFTB. Documentation such as FTB Pub.1436X 2018 Test Package for e-file of California Business, Individual, and Fiduciary Tax Returns and Stand-Alone Payments reveals some interesting details...

The purpose of PATS is to ensure, prior to “live” processing, that:

• Software Developers and Transmitters send submissions in the correct format, meet our electronic filing schema specifications, and have no business rule violations (rejects).

So there's a schema involved behind the scenes that the submitted return data needs to conform to. They also offer a test and production submission pipeline for developers to develop and validate against before submitting live returns for official submission of customer returns.

According to the various tables in the document there appears to be some support for receiving returns in the form of XML or PDF data, which gives a clue to what that data that flows into SWIFT file system must look like.

In conclusion: given all the above backend infrastructure and support for tax professionals and developers it appears that California indeed has e-file support, but they simply delegate the front end experience to third party software developers. There's no free general purpose application front end that's free online like Free File Fillable Forms. The state simply hasn't taken that on. And that begs the question. How exactly did the Federal government manage to originally get Intuit, and later On-LineTaxes, Inc. to build and maintain Free File Fillable Forms? Interestingly enough that new free file fillable forms provider has CA offerings https://www.olt.com/main/home/ca.asp

I'm not entirely sure how this works but there appears to be some mechanism for professional or high volume tax preparers in the so called California e-file Program.

Enroll in e-file program

Tax professionals

To automatically enroll in the California e-file Program:

1. Apply for the IRS Electronic Filing (e-file) Program. We will receive your account information within 2 weeks after the IRS accepts you into their program.
2. e-file with us:
   1. Tax preparers: Use your IRS-assigned Electronic Filer Identification Number (EFIN).
   2. Transmitters: Use your IRS-assigned Electronic Transmitter Identification Number (ETIN).
3. Comply with the guidelines found in the Handbook for Authorized e-file Providers (FTB Pub. 1345).

https://www.ftb.ca.gov/tax-pros/efile/enroll-in-efile-program.html

I'll try to learn more about the constraints surrounding this program and feed back here the findings.

I'm not entirely sure how this works but there appears to be some mechanism for professional or high volume tax preparers to electronically transmit in the so called California e-file Program.

Enroll in e-file program

Tax professionals

To automatically enroll in the California e-file Program:

1. Apply for the IRS Electronic Filing (e-file) Program. We will receive your account information within 2 weeks after the IRS accepts you into their program.
2. e-file with us:
   1. Tax preparers: Use your IRS-assigned Electronic Filer Identification Number (EFIN).
   2. Transmitters: Use your IRS-assigned Electronic Transmitter Identification Number (ETIN).
3. Comply with the guidelines found in the Handbook for Authorized e-file Providers (FTB Pub. 1345).

https://www.ftb.ca.gov/tax-pros/efile/enroll-in-efile-program.html

This is an interesting bit from the linked Handbook above...

Section 2 e­file Program

2.1 General Information

Our e-file program checks the return information for completeness and accuracy. If our e-file program accepts the return, you receive an acknowledgement (ACK) showing we accepted the return. If our e-file program rejects the return, you receive an ACK identifying the problem(s) that caused our e-file program to reject the return. You must correct the errors and retransmit the return for processing.

You may electronically transmit the return Forms 540, 540NR, 540 2EZ, 541, 100, 100S, 100W, 100X, 199, 565, and 568, via a transmitter or directly to us. Returns are transmitted to us via the Internet, using our Secure Web Internet File Transfer (SWIFT) system. Check with your software provider or transmitter if you have questions about submitting your returns.

We accept e-file returns for the following tax years:

• Individual e-file: 2021, 2020, and 2019
• Business e-file: 2021, 2020, and 2019
• Fiduciary e-file: 2021, 2020, and 2019

So there's definitely a backend that California has in place to receive an e-filed return, but there's no application front end that's just free online like Free File Fillable Forms.