TL;DR: A 24-person residential plumbing company in San Diego invoices 2,800 jobs per year. The billing process: a plumber writes job details on a clipboard, the clipboard rides in a van folder, the folder arrives at the office days later, and an admin deciphers the handwriting and enters it into ServiceTitan. Average time from job completion to invoice sent: 4.2 days. Thirty-four job sheets lost last year ($8,000-$12,000 in uninvoiced work). Fifteen to twenty percent of jobs have materials consumed but not listed ($18,000-$28,000 in annual leakage). We designed a four-stage agent: mobile completion form filled on-site in 3 minutes, validation that checks materials against job type while the plumber is still parked at the house, automatic invoice generation via ServiceTitan API, and a dashboard tracking completion-to-invoice time and materials variance. Invoice delay: 4.2 days down to 22 minutes. Running cost: $29-$90/month.
Thursday, 3:45pm, Kearny Mesa
Mike finishes a water heater replacement. He pulls out the clipboard. Writes: "Resi WH replacement. 50gal Rheem. Removed old unit. Installed new. Pressure relief valve replaced. Expansion tank inspected, OK. 3.5 hrs on site."
He takes a photo of the completed work on his phone (it stays on his phone). He notes the materials: "1x 50gal Rheem Pro, 1x PRV, copper fittings, Teflon, solder." He doesn't note the exact quantity of copper fittings because he's already thinking about the next call across town in Pacific Beach.
The clipboard goes in the van folder. Friday is busy: three calls, two emergencies. Saturday, two more. The van folder doesn't make it to the office until Monday morning.
Monday, 8:30am. Lisa opens the van folder. Four job sheets from Thursday and Friday. Two from Saturday. One from the previous Wednesday that fell behind the seat.
She starts with Thursday's water heater. Mike's handwriting is, in Lisa's diplomatic assessment, "interpretive." Is that a 50-gallon or a 30-gallon? She texts Mike. Mike is already on a Monday morning call. He responds 2 hours later: "50."
Lisa enters the job into ServiceTitan. Looks up the Rheem 50-gallon price. Adds the PRV. Adds "copper fittings" at a standard markup (she doesn't know the exact quantity Mike used, and neither does Mike at this point, four days later). Generates the invoice. Sends to the customer.
Total time from job completion (Thursday 3:45pm) to invoice sent (Monday 11:20am): 4 days, 19 hours. The customer pays on receipt. If they'd received the invoice Thursday evening, the company would have had the payment by Saturday. Instead, the payment arrives Wednesday.
Multiply by 2,800 jobs per year. This is, when stated precisely, a billing system whose data format is a clipboard, whose transfer mechanism is a van, whose processing speed is limited by traffic on the I-8, and whose quality control is Lisa's ability to distinguish Mike's fives from his threes.
The Company
Residential and light commercial plumbing company in San Diego. Twenty-four employees. $3.4M annual revenue. Roughly 2,800 jobs per year across 14 plumbers.
The numbers behind the van folder:
Average time from job completion to invoice sent: 4.2 days. Jobs exceeding 7 days to invoice: 22% (roughly 616 jobs per year). Admin time per job (deciphering, entering, matching materials, generating invoice): 18-25 minutes. Total admin time on quote-to-invoice processing: approximately 1,050-1,170 hours per year. Lisa and her colleague spend 50-55% of their working week on this. They were hired as office administrators. Half their job is being a human OCR system.
Lost or illegible job sheets in the prior 12 months: 34. Estimated uninvoiced revenue: $8,000-$12,000. Work that was performed, materials that were consumed, time that was spent, and none of it billed because a piece of paper fell behind a van seat.
Jobs where the plumber forgot to list materials used: 15-20%. The company absorbs the difference. Estimated annual revenue leakage from unbilled materials: $18,000-$28,000. Mike used six copper fittings. He wrote "copper fittings." Lisa billed for a standard estimate. The gap between six and the standard estimate, multiplied by 2,800 jobs, is the most expensive rounding error in the business.
Late invoicing impact on cash flow: estimated $45,000-$65,000 in delayed receivables at any given time. The money isn't lost. It's late. And late cash flow compounds into credit line usage and the owner checking the bank balance Monday mornings (a habit Marcus in Houston knows well).
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