The mistakes that get law firms into the most trouble aren’t complicated tax issues. They’re basic bookkeeping errors around trust accounting that can trigger bar complaints and worse.

Commingling operating and trust funds is the biggest one. Client funds in IOLTA accounts must stay completely separate from the firm’s operating money. When deposits land in the wrong account or transfers happen without documentation, the firm is commingling. It doesn’t matter if it’s accidental. State bars treat this seriously, and it’s one of the most common reasons attorneys face disciplinary action.

Paying firm expenses from the IOLTA account is closely related. Office rent, software, even a quick transfer to cover payroll when operating funds are short. Every dollar in the trust account belongs to a client until it’s properly earned and moved out through the correct process.

Deducting merchant fees from trust deposits catches many firms off guard. When a client pays a retainer by credit card, the processor takes its cut. If that fee reduces what hits the trust account, the firm just used client funds to pay a business expense. The full retainer amount needs to land in trust and the merchant fee needs to come from operating funds.

Skipping three-way reconciliation is how all of these problems go undetected. A proper three-way reconciliation compares the bank statement balance, the book balance, and the sum of individual client ledger balances. If those three don’t match, something is wrong. Many firms reconcile the bank to the books and stop there, never checking whether individual client balances add up to the trust total. That’s where shortages hide.

Beyond trust accounting, two operational mistakes quietly eat into profitability.

Not tracking unbilled work in progress means the firm doesn’t know how much billable effort is waiting to be invoiced. Time gets written off or forgotten entirely. Firms that treat unbilled WIP as a real financial metric bill more consistently and collect more of what they earn. Professional services bookkeeping should always include WIP tracking as part of the monthly process.

Mis-categorizing cost advances is equally common. When firms pay filing fees, court costs, or expert witness fees on behalf of clients, those are receivables that should be billed back. When they get lumped into general overhead, the firm absorbs costs it should be recovering and its profitability looks worse than it actually is.

Most of these mistakes happen because the person doing the books doesn’t understand how law firm finances differ from a typical small business. The fix is usually getting the chart of accounts, reconciliation process, and transaction workflows built correctly for how legal practices actually operate. Working with Beaver Dam accounting services experienced in trust accounting and legal billing can make a real difference in keeping a firm both compliant and profitable.