Comp benefits are supposed to arrive on a statutory clock. When they don’t, California stacks two very different penalties — one automatic, one litigated — and parties routinely confuse them. Here is the split, with the arithmetic computed.
§4650(d): the automatic 10%
If a TD or PD installment is paid late, the payer owes the installment plus 10% — self-executing, no fault required, no WCAB finding needed. It applies per late payment and is the everyday penalty. The calculator has a §4650(d) toggle that applies the 10% to the computed indemnity so demand letters and audits use the right number.
§5814: the litigated 25%
When payment of ANY class of benefit is unreasonably delayed or refused, the WCAB may increase the delayed amount by up to 25%, capped at $10,000 per violation. Unreasonableness is the whole fight: the payer must show genuine doubt of liability based on a reasonable investigation. Classic triggers — the late first TD check, benefits cut off without notice, an award simply not paid.
The arithmetic
Delayed 36% PD award ($50,170) → 25% = $12,542.50 → capped at $10,000
Two missed $800 TD checks → 25% of $1,600 = $400
The base amounts come straight from the schedule — the same engine-computed awards on the money chart and in the body-part money pages; TD rates are in TD vs. PD. Note the asymmetry: on small delays the 25% is modest, which is why §5814 fights cluster around whole delayed awards, not single checks.
Practical notes
Penalty exposure attaches to the class of benefit delayed (TD, PD, medical), multiple violations can stack separately, and a §5814 award also carries attorney-fee exposure under §5814.5 when an award was already in place. For payers: the paper trail of a real investigation is the defense. For applicants: the penalty petition rises or falls on the delay timeline — dates, amounts, notices. Both sides need the underlying indemnity computed exactly, which is what the calculator is for. Estimates for informational use; not legal advice.