When you are employed by someone else, they will usually take taxes off of each pay cheque. So when you do your income taxes you usually don’t have to pay much extra. When you are self-employed, you often don’t pay taxes though out the year, so you’ll have to pay it all at income tax time.
This is the same story for CPP. If you are self-employed, you must pay your CPP contribution if your income is high enough. This will be added to the amount you have to pay in income tax. https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-contributions/canada-pension-plan-cpp/cpp-self-employed.html
If you elected to Employment Insurance (EI), this will also be included in your income tax bill. https://www.canada.ca/en/services/benefits/ei/ei-self-employed-workers.html
You also may have other income that you are paying taxes on, or some type of repayment which may be adding to your total.
If you’re still not able to figure out where the $8000, go back over your review from the start (or at least the business portion) and make sure you’ve entered all the numbers correctly.
This happened to me when I put a fiscal period ending for my business that was NOT December 31. It added an extra form T1139B (I closed off my business on the 21st). It calculated the number of days prior to year ending (10) and said I continued my business AFTER the end of the day. Pro-rated the amount it THINKS I would have made in those 10 days...and added more income to my actual net income that I didn't make.
There are 2 Problems with this:
1) It should have been -10 days. Not 10 days. This field had to be overridden and excluded me from NetFile.
2) It doesn't make sense to pro-rate ANY income for self employed individuals because we don't usually HAVE steady pay. A lot of us have contracts that may or may not exist during the year. There may be 0 dollars of income for the following year. In my case I closed OFF my business so there won't be any income in the coming year for this business.
To get around this problem I put my fiscal ending date at December 31st and it removed this extra form. This created a new problem in that pensionable earnings (CPP) was 0 and the Net Income from this business was not copied to the T1 General slip properly.
I filled out the CPT20 (because my business contract provider did not operate in Canada or contribute CPP for me). I operated in Canada....from my home as a Canadian self-employed individual. It calculated my CPP correctly...
It DID not fix the NET Income or calculate my tax owned on business earnings. The Business Summary had a value for NET Income for business 1. This did NOT get copied correctly to the 13500 field at the bottom of this summary page.