The biggest mistake specific to roofing is lumping storm work and retail work into one revenue bucket. These are fundamentally different types of jobs. Storm work involves insurance claims, supplement negotiations, and longer collection timelines. Retail jobs are sold, completed, and paid on a more predictable schedule. When you combine them, you can’t tell which side of your business is actually profitable. You might think you’re doing great because storm season was busy, but your retail margins could be underwater. Track them as separate revenue categories so you can evaluate each one honestly.

Paying subcontractors without collecting W-9s first is another common problem. It feels like a minor paperwork detail when you’re trying to get a crew on a roof, but it becomes a real headache at year end. Without a W-9 on file, you don’t have the tax ID you need to file 1099s. And if you can’t file accurate 1099s, the IRS may disallow those subcontractor payments as deductions. Collect the W-9 before the first payment goes out. No exceptions. Make it part of your onboarding process for every sub, right alongside the insurance certificate.

Missing dump fees and disposal costs in construction job costing is quietly one of the most damaging mistakes. Tear-off generates a lot of waste, and dumpster rentals and landfill fees add up fast. If those costs aren’t coded to the specific job, your material and labor numbers look fine but your actual profit per job is lower than you think. The same goes for permit fees, delivery charges, and equipment rentals. Every cost that exists because of a specific job needs to be tracked against that job.

Commingling personal and business expenses is not unique to roofers, but it happens a lot in this trade. Using the business account to pay personal bills or running materials on a personal card without recording them creates a mess. Your financial statements become unreliable, your tax deductions are harder to defend, and your bookkeeper or accountant has to spend extra time untangling transactions that should have been clean from the start. Separate accounts and separate cards are worth the minor inconvenience.

Not reconciling merchant deposits correctly is a subtle mistake that throws off your cash balance. When a customer pays $10,000 by credit card, the processor deposits something like $9,700 after fees. If you record the full $10,000 as income but only $9,700 hits your bank account, you have a $300 discrepancy. Multiply that across dozens of transactions per month and your bank reconciliation never balances. Record revenue at the full invoice amount and book the processing fees as a separate expense. That way your income is accurate and your fees are visible.

These mistakes don’t usually show up as a single dramatic problem. They accumulate quietly until your books don’t match reality and you can’t trust your numbers for bidding, hiring, or tax planning. If your books have gotten away from you, Wisconsin small business bookkeeping services built around the trades can help you get back on track and set up systems that prevent these issues going forward.