The biggest mistake is commingling rental income and expenses with personal finances. Depositing rent checks into your personal checking account and paying property expenses from the same account makes it nearly impossible to know how your rentals are actually performing. Open a separate bank account for your rental business and run everything through it.

Not tracking income and expenses by individual property is another common problem. If you own multiple rentals, you need to see whether each one is profitable on its own. Lumping everything together hides underperforming properties. Your accounting software should be set up with each property as a separate class or location so you can pull a profit and loss statement for any single property.

Misclassifying repairs versus capital improvements costs landlords money at tax time. A repair fixes something that’s broken and gets deducted immediately. A capital improvement adds value or extends the useful life of the property and must be depreciated over multiple years. Replacing a broken faucet is a repair. Replacing all the plumbing in the house is an improvement. Getting this wrong means either paying too much tax now or creating problems if you’re ever audited.

Security deposits create confusion because they’re not income. When a tenant gives you a security deposit, that money belongs to them until you have a legitimate claim to it. Record it as a liability on your books, not as rental income. Only move it to income when you apply it to damages or unpaid rent. Treating deposits as income when received inflates your taxable income and misrepresents your financial position.

Many real estate investors also fail to track depreciation properly. Depreciation reduces your taxable income each year, but it also affects your cost basis when you sell. If you’re not tracking depreciation from the start, you’ll have trouble calculating gains at sale and may end up paying more capital gains tax than necessary.

Delayed bookkeeping is the mistake that enables all the others. When you wait months to categorize transactions and reconcile accounts, you forget what charges were for and errors go unnoticed. Reconcile monthly at minimum. Weekly is better if you have multiple properties or high transaction volume.

Finally, poor documentation creates problems you won’t discover until they matter. Keep records of tenant payments, repair invoices, and improvement costs. When the IRS asks why you deducted $4,200 in repairs on a property, you need to show what that money was spent on. Working with a QuickBooks bookkeeper in Santa Fe can help you build habits and systems that prevent these mistakes from compounding over time.