Supreme Court supplemental brief (new authorities): no later than 10 days before oral argument

10 days before date of oral argument in the supreme court, under Cal. Rules of Court, rule 8.520(d)(2).

Rule text

(2) A supplemental brief must not exceed 2,800 words, including footnotes, if produced on a computer or 10 pages if typewritten, and must be served and filed no later than 10 days before oral argument.

Cal. Rules of Court, rule 8.520(d)(2), official source

Calculate this deadline

Deadline
Tuesday, October 27, 2026
  1. Trigger (Date of oral argument in the Supreme Court): Friday, November 6, 2026.
  2. Count back 10 calendar days: Tuesday, October 27, 2026.
Rules applied
Cal. Rules of Court, rule 8.520(d)(2)
(2) A supplemental brief must not exceed 2,800 words, including footnotes, if produced on a computer or 10 pages if typewritten, and must be served and filed no later than 10 days before oral argument.
Official source
Cal. Rules of Court, rules 1.10, 8.60(a); Cal. Code Civ. Proc. 12, 12a, 12b
CRC 1.10(a): "The time in which any act provided by these rules is to be performed is computed by excluding the first day and including the last, unless the last day is a Saturday, Sunday, or other legal holiday, and then it is also excluded." CRC 1.10(b): "Unless otherwise provided by law, if the last day for the performance of any act that is required by these rules to be performed within a specific period of time falls on a Saturday, Sunday, or other legal holiday, the period is extended to and includes the next day that is not a holiday." CRC 8.60(a): "The Code of Civil Procedure governs computing and extending the time to do any act required or permitted under these rules." CCP 12: "The time in which any act provided by law is to be done is computed by excluding the first day, and including the last, unless the last day is a holiday, and then it is also excluded." CCP 12a(a): "If the last day for the performance of any act provided or required by law to be performed within a specified period of time is a holiday, then that period is hereby extended to and including the next day that is not a holiday. For purposes of this section, “holiday” means all day on Saturdays, all holidays specified in Section 135 and, to the extent provided in Section 12b, all days that by terms of Section 12b are required to be considered as holidays." CCP 12b: "If any city, county, state, or public office, other than a branch office, is closed for the whole of any day, insofar as the business of that office is concerned, that day shall be considered as a holiday for the purposes of computing time under Sections 12 and 12a."
Official source
  • Limited to new authorities, legislation, or matters not available in time for the merits brief (8.520(d)(1)). Backward count: if the 10th day before falls on a weekend or holiday, file on the preceding court day (conservative).
  • If the clerk's office is closed or inaccessible on the last day (weather, emergency or local closure orders), the deadline may be extended. Check local orders.

This calculator applies the cited rules to the dates you enter. It is not legal advice. Court orders, local rules, and case-specific facts can change a deadline; verify before relying on it. Rule set pending attorney review.

Worked example

Date of oral argument in the Supreme Court on Monday, March 15, 2027, personal service: due Friday, March 5, 2027.

  1. Trigger (Date of oral argument in the Supreme Court): Monday, March 15, 2027.
  2. Count back 10 calendar days: Friday, March 5, 2027.

Notes

Limited to new authorities, legislation, or matters not available in time for the merits brief (8.520(d)(1)). Backward count: if the 10th day before falls on a weekend or holiday, file on the preceding court day (conservative).

Related deadlines

All California appeals and writs deadlines

Rules current as of 2026-10-23. Confirm against the official source and any local rule or court order before relying on a date. Rules changelog.