3 Common Bookkeeping Mistakes Small Business Owners Make

Some bookkeeping mistakes are small and easy to fix. Others compound quietly until they show up at tax time, during an audit, or in the middle of a year you were trying to grow. The three below land in the second category. They cause real problems for small business owners, and all three are avoidable once you know what to watch for.

Mixing Personal and Business Money

This one shows up constantly, especially in the early days. You buy office supplies on your personal card, your business reimburses your phone bill, you grab lunch with your business debit because that's the card in your wallet. Each individual instance feels harmless. The cumulative effect is a mess.

When personal and business transactions live in the same account, separating them at year-end takes hours you didn't plan for. You're sifting through statements, second-guessing receipts, and rebuilding context from memory. You also lose accuracy. The things you forget about become things you under-deduct or over-deduct, and either direction has a cost.

There's a legal angle too. If you're set up as an LLC or corporation, one of the main reasons you went through that paperwork is to keep your personal assets protected from business liabilities. Commingling funds undermines that protection. In the worst case, a court can find that the separation was never real and reach through to your personal savings or property. The technical term is "piercing the corporate veil," and it's the kind of thing you don't want to learn about during a lawsuit.

The fix is not complicated. Open a dedicated business checking account. Get a business debit card. If you can qualify for a business credit card, get one of those too. Run all business income and expenses through those accounts only. When you need to pay yourself, transfer money from business to personal in a single clean transaction and categorize it as an owner's draw. When the business needs to reimburse you for something you paid out of pocket, do that in a single clean transaction too.

If you're already commingled and dreading the cleanup, this guide to setting up QuickBooks Online covers how to start fresh, and this chart of accounts post can help you organize what's there. Clean separation is also one of the simplest things that protects your business from fraud.

Paying Contractors Before Collecting a W-9

If you pay anyone $600 or more for services in a year and they're not a W-2 employee, you're probably going to need to issue them a 1099-NEC in January. To do that, you need their legal name, address, and tax ID, all of which live on a W-9. The rule of thumb is simple: collect the W-9 before you cut the first check.

What goes wrong is predictable. You hire someone for a project, the work goes well, you pay them, and you don't think about it again until January, when you're trying to issue 1099s and realize you don't have W-9s for half your contractors. Now you're chasing people down for tax information months after the fact. Some won't respond. Some will have moved or changed their email. Some will be annoyed that you're asking now instead of then. The IRS doesn't care about any of that. You still need to file.

There are penalties for failing to file or filing late, and additional penalties for filing with incorrect information. Incorrect filings are more likely when you're scrambling. Beyond compliance, this is a professionalism thing. Asking for a W-9 upfront signals that you take your business seriously, and most legitimate contractors expect to be asked.

The fix is to make collecting a W-9 part of your onboarding for any contractor, before any money moves. The form is free and downloadable from the IRS. Keep signed copies somewhere you'll find them again in eleven months.

Picking Software You'll Outgrow in Six Months

A note before this one: this section is about a specific QuickBooks product and the situations where it doesn't fit. Skip ahead if software choice isn't where you are right now.

When you're starting out and money is tight, the cheapest option in a software lineup is tempting. For QuickBooks, that's currently QuickBooks Solopreneur (which replaced the discontinued QuickBooks Self-Employed in 2024). Solopreneur is around $20 a month, it's marketed at exactly the people reading this post, and on the surface it looks like the obvious choice.

Here's what the marketing doesn't emphasize. Solopreneur is a stripped-down product. It runs three reports (profit and loss, balance sheet, and an account quick report) and that's it. You can't customize the chart of accounts in any meaningful way. It supports one user, with no real way to give your bookkeeper or accountant proper access. Categories are limited to a fixed set. If your business has any complexity at all, or if you plan to grow, you will hit those limits fast.

QuickBooks Online Simple Start runs about $38 a month. That's $18 more than Solopreneur, which sounds like a lot in percentage terms and is barely anything in actual dollars. For that $18 you get a real chart of accounts, real reporting, the ability to invite an accountant, and a product you can actually grow into. Migrating from Solopreneur to Simple Start is smoother than it used to be (Solopreneur is now built on the same platform as the rest of QBO), but you still don't want to be making that switch in the middle of tax season because you ran into a wall.

Solopreneur can genuinely be the right call for a very simple sole proprietorship with one income stream and no plans to expand. For most of the people I work with, it isn't. If you're trying to figure out whether you need software at all, this spreadsheets vs QuickBooks comparison is a good place to start.

A Note on All Three

These mistakes have something in common - none of them happen because someone is careless. They happen because bookkeeping is the part of running a business that's easiest to push to "later," and "later" turns into a problem you're solving under pressure.

If you want a hand sorting out books that already have one or more of these issues, you can book a free call. (If you're not sure yet whether outside help makes sense, my post on when to hire a bookkeeper walks through the signs!)