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    There are several reasons to conduct your business with proper contracts.  One is making sure that your duties, the scope of your  performance, is well defined.  The other is to ensure that you will receive what you bargained for - in other words, get paid.
    When you bid on municipal work your contract is generally the bid package.  It contains your contract terms which will include your contract price.  It will also provide, as do most institutional contracts, that any extra work you perform must be approved in advance in writing, or you don't get paid.  A recently decided case caught my attention and should be of interest to you.   G. VOSKANIAN CONSTRUCTION, INC., v. ALHAMBRA UNIFIED SCHOOL DISTRICT, [ COURT OF APPEAL OF CALIFORNIA, SECOND APPELLATE DISTRICT, DIVISION THREE,  204 Cal. App. 4th 981; 2012 Cal. App.,  March 29, 2012, Opinion Filed] is a rather long decision that has a few holdings of interest.  First, the case holds that there can be no waiver of the contract requirement that extras be approved in writing if you want to get paid, and that the provision could not be waived by conduct of the parties (which earlier cases had held).
    What happens when the plans and specifications provided by the municipality are wrong and the contractor, in this case a fire alarm contractor, has to perform extra work, and does so without a written extra work order?  In this case the court awarded compensation. Here's what the court had to say:
    "  In soliciting bids for the fire alarm system for the portable buildings at the school campus, the District required bidders to submit their bids based on the  [**22] plans and specifications prepared by the District's architect. After Voskanian was awarded the fire alarm contract, it discovered that many of the portable buildings had more rooms than shown on the plans, thus requiring more alarm devices, conduit and wiring. For example, one of the buildings was shown on the plans as a single room with no interior walls; however, as built, that structure had six interior rooms. Due to the error in the plans, Voskanian requested an additional $39,777 for extra work on the fire alarm contract, over and above the original $55,000 contract price.

   Thus, Voskanian's entitlement to recover for extra work performed in connection with the fire alarm contract does not turn upon the issuance of written change orders. Because the extra work on the fire alarm contract was necessitated by incorrect plans and specifications furnished by the District, under settled law Voskanian was entitled to recover for said work."

    A good outcome by the fire alarm contractor.  Whether you're bidding a job or negotiating for the job, be certain to understand your contract terms.  Confusing terms or failing to comply with terms could end up costing you time and money to engage in litigtation to recover money you believe you're entitled to.
    I'll post the entire decision on my web site at leading cases.  Find it under California cases.  https://www.kirschenbaumesq.com/page/alarm-law-issues
    The Standard Fire All in One by the way deals with AHJ changes after the contract is signed this way - the subscriber is required to pay all changes required by the AHJ.