Bookkeeping is the boring foundation that makes everything else in your business decisions reliable. Pricing decisions, tax filings, loan applications, hiring decisions — they all depend on whether you actually know what came in, what went out, and what you're sitting on. This guide covers the small set of bookkeeping concepts an owner genuinely needs to understand, even if a bookkeeper or accountant does the day-to-day work.
What Bookkeeping Actually Produces
Bookkeeping is the engine that produces three financial statements:
- Profit & Loss (Income Statement). Revenue minus expenses over a period. Did the business make money this month?
- Balance Sheet. Assets, liabilities, and equity at a point in time. What does the business own and owe right now?
- Cash Flow Statement. How cash actually moved — operations, investing, financing. Where did the money go?
If bookkeeping is sloppy, all three statements lie, and every decision you make using them is downstream of that lie.
Single-Entry vs Double-Entry
Single-entry bookkeeping records each transaction once. It looks like a chequebook register: date, description, amount in or out, running balance. It's fine for a freelancer with one bank account and no inventory. It breaks the moment you have AR, AP, payroll, or anything resembling a real balance sheet.
Double-entry bookkeeping records each transaction twice — once as a debit, once as a matching credit — so total debits always equal total credits. This sounds bureaucratic but it has a critical property: if your books don't balance, you have an error you can find. Single-entry can be wrong forever without you noticing.
| Transaction | Debit account | Credit account |
|---|---|---|
| Customer pays $500 invoice | Cash $500 | Accounts Receivable $500 |
| Buy $300 of supplies on card | Supplies Expense $300 | Credit Card Payable $300 |
| Pay $1,200 rent | Rent Expense $1,200 | Cash $1,200 |
| Invoice client $2,000 | Accounts Receivable $2,000 | Sales Revenue $2,000 |
The Chart of Accounts
Every transaction is categorised into an account on the chart of accounts (COA). A clean COA has 5 sections, each numbered:
- 1000s — Assets. Cash, AR, inventory, equipment, prepaid expenses.
- 2000s — Liabilities. AP, credit cards, loans, payroll taxes payable.
- 3000s — Equity. Owner's capital, retained earnings, distributions.
- 4000s — Revenue. Product sales, service revenue, interest income.
- 5000s+ — Expenses. Cost of goods sold, payroll, rent, software, marketing.
Mistakes that make a COA useless: too many accounts (every vendor has its own line), too few accounts (one giant "Miscellaneous"), or inconsistent categorisation (the same expense in three different accounts depending on who entered it). Aim for 30–80 accounts for a typical small business. Anything outside that range usually signals trouble.
Cash vs Accrual
The accounting basis determines when revenue and expenses are recognised.
| Cash basis | Accrual basis | |
|---|---|---|
| Revenue recognised | When cash is received | When the work is delivered |
| Expenses recognised | When cash is paid | When the expense is incurred |
| Best for | Sole proprietors, no inventory, simple cash businesses | Anything with AR/AP, inventory, investors, or significant complexity |
| Required when | Below revenue thresholds in most jurisdictions | Public companies, audited entities, businesses with inventory, US revenue >$26M (varies) |
Many small businesses are on cash basis with their accountant but produce internal P&Ls on accrual — because cash-basis P&L is misleading whenever your invoicing and payment timing don't line up.
The Monthly Close
The monthly close is the ritual where you confirm the books are right. A complete close has 8 steps:
- Bank reconciliation. Match every transaction in your books against the bank statement. Investigate every difference. The book balance and the bank balance must match after timing items.
- Credit card reconciliation. Same exercise for each card.
- AR review. Run the aging. Flag anything 30+ days late.
- AP review. Confirm bills entered match what's coming due.
- Payroll accrual. Confirm wages, taxes, and benefits are accrued through period-end.
- Inventory count. Adjust inventory to physical count (if applicable).
- Depreciation. Record monthly depreciation on capital assets.
- Review financials. Print P&L and balance sheet. Compare to prior month and budget. Investigate variances.
The whole close should take 2–5 days. Anything over a week usually means transactions are being miscategorised throughout the month.
The Five Most Common Bookkeeping Mistakes
- Mixing personal and business money. The single most damaging mistake. Open a separate business bank account on day one, even as a sole proprietor.
- Using "Owner Draw" as a catch-all. When you pull money out for legitimate business expenses but record it as owner draw, you lose the deduction.
- Not reconciling. Books that look right but haven't been reconciled to the bank are often wrong by thousands.
- Categorising taxes as expenses. Sales tax collected from customers isn't revenue — it's a liability. Payroll tax withheld from employees isn't an expense — it's a liability.
- Letting it pile up. Three months of unsorted receipts before year-end is the most expensive way to do bookkeeping; your accountant charges premium rates for cleanup, and you'll miss deductions.
DIY, Software, Bookkeeper, or Accountant?
- DIY with spreadsheets. Only for solo, single-account, very low transaction volume. Below ~$50K revenue.
- Self-serve software (QuickBooks Self-Employed, Wave, FreshBooks). Works for solo and very small teams, $50K–$300K.
- Full software (QuickBooks Online, Xero, Sage) + part-time bookkeeper. The right setup for most growing businesses, $300K–$5M.
- Full bookkeeper + CPA-supervised close + annual audit (if needed). Above $5M or pre-investment.
Try It Yourself
Calculate true profit margin from your books — see what each sale actually contributes after all costs.
Profit Margin Calculator →