Every business needs bookkeeping, from a one-person shop to a large company. Doing your own books can look simple and cheap. But there is a lot of room for error. Small mistakes can cost you deductions, trigger IRS penalties, and hide cash problems until it’s too late.

Below are the six most common bookkeeping mistakes we see, and how to avoid each one.

Who is this guide for?

This guide is for US small business owners, freelancers, and startup founders who keep their own books or work with a part-time bookkeeper.

Use it when you:

  • Are setting up bookkeeping for a new business
  • Are preparing for tax season or a possible IRS review
  • Are hiring your first employees or contractors
  • Have started selling online to customers in other states
  • Want to check whether your current books are audit-ready

What do we find when we review a new client’s books?

Every new ProfitsView client starts with a review of their last 12 months of books. We check the same six areas each time, so we can compare one business against the next. In our experience, the results follow a clear pattern:

  • Reconciliation is the most common gap. It is usually the first thing we have to fix, often across several months at once.
  • Missing receipts come next. Small expenses are the ones most often recorded with no receipt or business purpose.
  • Sales tax issues grow with online sales. Businesses selling into several states are the ones most likely to have sales tax recorded as revenue.
  • Worker classification is the least common, but the costliest. When we do find it, it takes the most time to correct.

What we’ve learned is that these mistakes rarely happen alone. A business that skips reconciliation usually has receipt gaps too, because nobody is reviewing the books each month.

1. Why should you keep receipts under $75?

Many owners throw away small receipts. They assume the IRS doesn’t need them. That’s only partly true. For travel, gift, and transportation expenses, the IRS doesn’t require a receipt for items under $75. Lodging is the exception: you need a receipt at any amount (IRS Publication 463).

You still have to prove the expense, though. Without a receipt, you need another record of the amount, date, place, and business purpose. Small receipts also support deductions that add up over a year.

How to avoid it:

  • Keep every receipt, whatever the amount.
  • Use digital accounting solutions that let you photograph a receipt and match it to the transaction.
  • Note the business purpose on the receipt or in the app.

2. Why do you need to track reimbursements?

Some expenses you pay on a client’s behalf can be billed back to them. Because they will be reimbursed, owners often forget to record them. That’s a mistake. Unrecorded reimbursable costs are easy to forget to invoice. They can also cost you deductions when the client never pays.

How to avoid it:

  • Record every reimbursable expense when you pay it, with the client’s name.
  • Use an expense-tracking app to tag billable costs automatically.
  • Review unbilled expenses before you send each invoice.

3. What happens if you misclassify employees?

Businesses work with employees, independent contractors, consultants, and freelancers. Each type is taxed differently. If you treat an employee as a contractor, you may owe back payroll taxes, plus penalties and interest.

The IRS uses common-law rules to decide worker status. It looks at three areas: behavioral control, financial control, and the type of relationship (IRS: Independent contractor or employee?). No single factor decides it. The whole relationship matters.

How to avoid it:

  • Review each worker against the IRS’s three categories before they start.
  • Keep signed contracts that describe how the work is controlled.
  • If you’re unsure, file Form SS-8 to ask the IRS for a determination.

4. Why is skipping bank reconciliation a problem?

Bank reconciliation means matching your books to your bank and card statements. It is one of the most important checks in bookkeeping. It catches bank errors, duplicate charges, and missing transactions early. It also shows how much cash you really have.

When reconciliations slip, small errors stack up. After a few months, the balance in your software no longer matches the bank, and fixing it takes much longer.

How to avoid it:

  • Reconcile every bank and credit card account at least once a month.
  • Investigate any difference right away, even a small one.
  • If reconciliation keeps falling behind, work with an experienced bookkeeper.

5. How long should you keep backup records?

Going fully paperless is convenient, but it’s risky without backups. A software failure or lost account can wipe out records you need for an audit. The IRS expects you to produce your records when asked, in paper or electronic form.

How long you keep records depends on the situation (IRS: How long should I keep records?):

  • 3 years for most income tax records
  • 4 years for employment tax records, after the tax is due or paid, whichever is later
  • 6 years if you left out income of more than 25% of the gross income shown on your return
  • 7 years if you claim a loss from worthless securities or a bad debt deduction
  • Indefinitely if you didn’t file a return or filed a fraudulent one

How to avoid it: Keep a second backup of every financial record, either in a separate cloud account or on paper. For most small businesses, keeping everything for 7 years covers all the common cases.

6. Are you collecting the right sales tax?

Online selling has made sales tax much harder for small businesses. In 2018, the US Supreme Court ruled in South Dakota v. Wayfair that states can require sellers to collect sales tax even without a physical presence in the state (Supreme Court opinion). Most states now have economic nexus rules based on your sales into that state.

A common mistake is recording total sales without separating out the sales tax collected. The tax then looks like income, and the bill arrives as a surprise.

How to avoid it:

  • Record sales tax collected in its own liability account, not as revenue.
  • Check each state’s nexus rules as your online sales grow.
  • Review sales tax rules with your bookkeeper every quarter, because they change often.

What do these mistakes cost if you miss a tax deadline?

Many of these mistakes lead to late or wrong tax filings. The IRS penalties for that are steep (IRS: Failure to file penalty):

  • Failure to file: 5% of the unpaid tax for each month or part of a month the return is late, up to 25%.
  • Failure to pay: 0.5% of the unpaid tax for each month or part of a month, up to 25%.

Rule Figure Source
Late filing penalty 5% of unpaid tax per month, up to 25% IRS
Late payment penalty 0.5% of unpaid tax per month, up to 25% IRS
Records retention, most income tax records 3 years IRS
Records retention, employment tax records At least 4 years IRS
Records retention, bad debt or worthless securities 7 years IRS
Online sales tax ruling (South Dakota v. Wayfair) 2018 U.S. Supreme Court

Here is how fast this adds up. A return filed 3 months late picks up a 15% failure-to-file penalty on the unpaid tax. After 5 months, it hits the 25% maximum. Clean, up-to-date books are the simplest way to avoid both penalties.

How did we clean up an online store’s books? (Example from our work)

This is a representative scenario based on the bookkeeping clients we support. Details are generalized to protect client confidentiality.

Situation: An online store selling into several states had done its own books for two years. Bank accounts hadn’t been reconciled for about 6 months. Sales tax was recorded as part of revenue, and small receipts were missing for most months.

What we did:

  • Reconciled all 6 months of bank and card statements, one month at a time.
  • Moved collected sales tax out of revenue and into its own liability account.
  • Checked which states the store had crossed the economic nexus threshold in.
  • Set up receipt capture so each expense is photographed and matched when it happens.

What changed: The books matched the bank again. Revenue was no longer overstated by the sales tax. The owner knew exactly which states needed registrations. From then on, a monthly reconciliation kept the books current instead of falling months behind.

In our experience, a cleanup like this is the point where owners first see their real profit, not just their bank balance.

How can you avoid bookkeeping mistakes?

Most bookkeeping mistakes come from the same root cause: records that aren’t kept up as you go. Keep every receipt, track reimbursements, classify workers correctly, reconcile every month, back up your records, and stay on top of sales tax.

If you would rather hand this off, ProfitsView’s bookkeeping services keep your books accurate and audit-ready every month. Talk to our team to get started.