Almost every startup makes the same five accounting mistakes, and almost none is serious at first. The problem comes with the first round: an investor asks for the accounts, the cap table or the months of runway, and there is no clear answer. Here are the five, why they happen and how to avoid them with no more than a few hours a month.
Mixing personal and company finances
What happens. You pay for the company’s software with your card, or a personal dinner with the company’s. By year end nobody remembers what was what.
Why it happens. At the start, you are the company. It is the quickest option and seems harmless.
How to avoid it. An account and a card just for the company from day one. If you pay for something of the company with your own money, keep the invoice in the company’s name and claim the refund. Without an invoice in its name, the company cannot deduct the VAT or the expense.
Leaving the books until year end
What happens. In December there are twelve months of unreconciled statements, missing invoices and expenses nobody can explain. And in Spain VAT is filed every quarter: without up-to-date books, form 303 is done blind.
Why it happens. The product always seems more urgent. And bookkeeping does not warn you when it falls behind.
How to avoid it. One hour a month, always on the same day: upload invoices, check the bank and clear up questions. If we handle it, we write to you before each quarter with what we need.
Keeping the cap table in a spreadsheet nobody updates
What happens. The cap table, the table of who holds how many shares, lives in a spreadsheet from two capital increases ago. The team’s equity agreements are in an email.
Why it happens. Each transaction is done in a hurry and the record is left for later.
How to avoid it. Update it at the time of each transaction: capital increase, convertible loan, shares for the team. And check that it matches the deeds and the Commercial Registry. A clear cap table is your best introduction in a round.
Not setting aside money for taxes and contributions
What happens. The corporate tax instalment, the quarter’s VAT or the month’s social security arrives, and there is no money set aside.
Why it happens. The VAT you charge your clients is not yours: you pay it to the Tax Agency every quarter. And taxes and contributions are paid after you get paid. Meanwhile, that money looks available.
How to avoid it. Each month, set aside the VAT you have charged, the withholdings from salaries and a share for contributions and corporate tax. If your startup has emerging company certification, it pays 15% in its first profitable year and the three following ones. We tell you the exact figure for your case.
Not watching cash flow
What happens. You know how much is in the bank, but not how many months you have left. The round is delayed by three months and the account does not hold out.
Why it happens. The bank balance is easy to check. Calculating the months of runway (cash available divided by net monthly spend) requires up-to-date figures. Late bookkeeping, again.
How to avoid it. Check three figures every month: cash available, net spend for the month and months remaining. Start preparing the next round when you have 9 to 12 months left, not 3.
Your five-point checklist
- Separate account and card for the company.
- One hour of bookkeeping a month, always on the same day.
- Cap table updated with every transaction.
- VAT, withholdings and taxes set aside every month.
- Months of runway calculated every month.
If you want to review the five points with your specific case, our startup advisory does it with you: cap table, valuation and preparing your next round.
Figures checked against official sources on 29 October 2026. They change every year, so confirm them before you act.