Most small business owners didn't start their company to manage spreadsheets. You started it because you're good at what you do — whether that's roofing, plumbing, running a restaurant, or consulting. Bookkeeping is the thing that keeps getting pushed to the back burner.
The problem is that small bookkeeping errors compound over time. What starts as a missed receipt in January can turn into a surprise tax bill or a cash crunch by December. After years of working with small business owners across Montana, these are the five mistakes I see most often — and what you can do right now to fix them.
Mixing Personal and Business Finances
This is the most common and most damaging mistake. When personal and business expenses run through the same account, it becomes nearly impossible to know what your business actually costs to run. It also creates real problems at tax time — and raises red flags if you're ever audited.
Open a dedicated business checking account if you haven't already. Even a free business checking account at a local credit union works. Every business expense goes on the business card, every personal expense stays personal. It takes one afternoon to set up and saves you hours every month.
Not Reconciling Your Accounts Monthly
Reconciling means comparing your bookkeeping records to your actual bank statements to make sure they match. Skipping this step means errors, duplicate charges, or even fraud can go unnoticed for months. By the time you catch it, untangling the mess is a major project.
Set a recurring reminder on the first week of every month to reconcile the previous month. If you use QuickBooks, the reconciliation tool walks you through it step by step. If it feels overwhelming, that's a good sign it's time to bring in a bookkeeper.
Losing Track of Receipts and Documentation
The IRS requires documentation for business deductions. If you're claiming a vehicle, meals, tools, or equipment and you don't have receipts to back it up, those deductions are at risk. Shoebox accounting — stuffing receipts in a drawer and dealing with it later — is a liability.
Use your phone. Apps like QuickBooks, Expensify, or even just a dedicated Google Drive folder let you photograph receipts the moment you get them. The best time to document an expense is right when it happens — not three months later.
Categorizing Expenses Incorrectly
Miscategorized expenses distort your financial picture. If you're running a roofing business and you categorize materials as office supplies, your reports won't reflect your true cost of goods sold — which means your profit margins are wrong, and your tax return could be inaccurate too.
Set up a chart of accounts that actually reflects your business at the start of the year. Take an hour to review your categories and make sure they make sense for what you do. When in doubt, ask a bookkeeper — getting this right from the start saves significant headaches later.
Only Looking at Your Books at Tax Time
If the only time you open QuickBooks is when your accountant asks for your records in April, you're flying blind for the other eleven months of the year. You can't make good business decisions without knowing your current financial position — what you're owed, what you owe, and whether you're actually profitable.
Review a simple profit and loss report at least once a month. It doesn't need to take more than 15 minutes. Look at revenue, look at expenses, and ask yourself if the numbers make sense. Consistent monthly reviews make tax season a non-event instead of a fire drill.
"Good bookkeeping isn't about being an accountant. It's about having enough visibility into your business to make confident decisions."
The Bottom Line
None of these mistakes are unusual — and none of them mean you're bad at running your business. They're just the natural result of being busy and focused on the work rather than the paperwork. The good news is that every one of them is fixable, often with a single afternoon of cleanup and a few new habits going forward.
If you're based in the Flathead Valley or anywhere in Montana and you're not sure where your books stand, I'm happy to take a look. A free 30-minute consultation costs you nothing and usually surfaces at least one or two things that can save you money before the next tax season.
Not Sure Where Your Books Stand?
Get a free 30-minute consultation with AJM Consulting. We'll take an honest look at your current setup and tell you exactly what needs attention.
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