can't efile as I get an error to write in text for line 76 ob firn 540

To resolve the error, go back through your CA state return interview. Within TurboTax, select State Taxes, then select Edit next to California, then select Go over California again and answer all of the questions. Double-check the line item number in the error notice if you don't have children on your return.

Line 76 of Form 540 for 2023 is the Young Child Tax Credit (YCTC):

The Young Child Tax Credit (YCTC) provides up to $1,117 per eligible tax return for tax year 2023. YCTC may provide you with cash back or reduce any tax you owe. California families qualify with earned income of $30,931 or less.  See here for more information.