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Bookkeeping affects your taxes because your return can only claim what your records can back up. Say you net $80,000 as a sole proprietor in Ontario. Income tax and CPP come to $22,126.47 by our calculator. If sloppy books leave you reporting $85,000 instead, that bill grows to $23,890.37, so five thousand dollars of forgotten costs hands the CRA $1,763.90 for nothing.
That’s the whole link, really. Good books show your real profit, your real GST/HST and your real payroll, and everything else follows.
What does the CRA expect you to keep?
The CRA calls them records: all your accounting and other financial documents. Sales, purchases, payroll, vehicle logs and GST/HST information all count. Paper or electronic is fine, as long as you can produce them.
Generally, you must keep all required records and supporting documents for a period of six years from the end of the last tax year they relate to.
Where to keep your records, for how long and how to request the permission to destroy them early, Canada Revenue Agency, canada.ca
| Rule | What the CRA says |
|---|---|
| How long to keep records | Six years from the end of the last tax year they relate to |
| Where to keep them | At your place of business or home in Canada, unless the CRA gives written permission otherwise |
| Records kept only outside Canada | Not counted as Canadian records, even if you open them online |
| Destroying records early | Only with written permission (Form T137) |
| Property bought or sold, business wound up | Longer periods apply |
The third row catches people who use software hosted abroad. Find out where your provider stores the files before you treat it as your only copy. The six years can run longer. The CRA says records of long-term property you bought or sold, and share registers, may need to be kept indefinitely, and for a late-filed return the six years count from the date you file it. If a return is under objection or appeal, keep the records until it is settled.
How can messy books cost you money?
Three ways, mostly. You forget expenses, so profit looks bigger than it is. You claim something you can’t prove and lose it in a review. Or you pay late because nobody knew the amount was coming.
The first is the quiet one, because no notice arrives saying you overpaid.
Go back to the $80,000 case. The self-employed tax calculator shows $13,233.57 of income tax and $8,892.90 of CPP (both halves), so you keep $57,873.53. Enter $85,000 and you keep $61,109.63 of a bigger number, but the extra $5,000 costs $1,764 in tax and CPP, and it was never profit. Watch one quirk: in that tool, deductions lower income tax but not CPP, and EI isn’t included, so your real bill can differ.
Do your books change what you owe during the year?
Yes, more than most people expect. Current books tell you the tax you’ll owe before the year ends, and that number decides if instalments apply to you. The CRA says you may need to if your net tax owing is over $3,000 ($1,800 in Quebec) for 2026 and in either 2025 or 2024. Instalments are due March 15, June 15, September 15 and December 15, except for farmers and fishers, who have one date on December 31. The tax instalments calculator splits an expected $9,000 into four payments of $2,250.
GST/HST has its own clock. Monthly and quarterly filers file and remit one month after the period ends, so your books must show the tax you collected and the tax you paid on purchases by then. The GST/HST calculator checks a single sale, and your books do the adding.
What should you set up first?
A separate business bank account. It’s dull and it removes most of the sorting later. After that, a habit: record each sale and cost within the week, and keep the receipt (or a photo of it) with a note on what it was for.
If you have staff, give payroll its own line. On $3,000 gross every two weeks in Ontario, the payroll remittance calculator shows $961.03 to send the CRA per pay period, and $228.41 of that is your share as employer. It’s a cost of hiring, so it belongs in your expenses.
What should a year-end bookkeeping checklist include?
- Every bank and credit card statement for the year, matched to your records.
- Sales invoices and a total for the year, split by GST/HST collected.
- Receipts for each expense, sorted by type, with a note for anything you can’t explain.
- A mileage log if you claim a vehicle, and the starting and ending odometer readings.
- Payroll summaries and the amounts you remitted to the CRA.
- A list of assets you bought, since some costs are claimed over several years.
- Your instalment payments for the year, so you do not count them twice.
With that pile in order, your accountant or your return software has what it needs. For small habits that keep the pile from growing, see bookkeeping habits for small business. For what you can claim, read business expenses the CRA accepts, and for the basics, basic bookkeeping.
How do bookkeeping and accounting work together on deductions?
Bookkeeping records each sale and cost as it happens. Accounting then turns those records into financial statements and a tax return, and an accountant can only claim the deductions your books can show. A deduction lowers the profit you report, so a receipt that is missing from the file is a deduction nobody can support later. That is why the order matters: get the records right first, then ask an accountant to manage the filing. Current books also help you understand your financial position and make decisions during the year, such as how much to set aside for tax, which finance choices you can afford and when to work out an instalment.
What if your books are behind right now?
Catch up before you file, not after. Start with the bank statements for the year, list every deposit and payment, and sort them into sales, expenses and personal. Anything you can’t explain gets set aside with a note. Mixing personal and business spending is the big one. Next comes recording a payment to the CRA as an expense when it’s really a payment toward tax you owe. Others: no receipt for a cash cost, no mileage log behind a vehicle claim, and books that quietly stop in October. Record keeping rules come from the CRA‘s business record keeping pages, read in September 2026 and checked again in November 2026. Instalment rules and 2026 due dates come from the CRA page on who has to pay tax instalments. Tax and CPP figures come from the 2026 federal and Ontario data in our calculators. Filing dates for the 2026 tax year weren’t posted yet when we checked, so confirm them with the CRA before you plan around them. We’re an independent site, not part of any government. Electronic records are accepted. But the CRA says records held only outside Canada and reached online aren't treated as Canadian records, so check where your provider stores them. No. You need records you can back up. A bookkeeper only saves you the time and the missed expenses. It can. Your year to date profit tells you if you'll owe more than $3,000, which is when instalments may apply. You may lose claims you can't support and pay more tax. We couldn't confirm penalty amounts for every case, so read the CRA's page on your situation. For information only. We provide no services, consultations or registrations, and we do not represent the CRA, any government or any other organization. We copy information by hand from official websites, so we can make mistakes and the data can go out of date. Please confirm everything with a certified professional, such as a chartered professional accountant, or on the official government websites before you rely on it. We do not guarantee that it is accurate, complete or current, and we accept no liability for how you use it. Official government websites · Full disclaimer Six years from the end of the last tax year they relate to, according to the CRA. Records for long-term property, or for a late-filed return, can need longer. To destroy records early you need written permission, which you ask for on Form T137. How tax works when you are self-employed in Canada: reporting income and expenses, paying both halves of CPP, instalments and when to register for GSTBookkeeping mistakes that show up in reviews
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