I just posted this reply in response to my original post, but in case this is still helpful, this is all the info that I have so far.

T2125B = business income

T2125P = professional income

T2125C = commission income

T2042 = farming income

T2121 = fishing income

The numbers 1-4 in each category correspond to the numbered business or professional activity you have listed. So if you are self-employed and only have one business, choose T2125B #1. If you have multiple, T2125B #1 for income related to Business 1 and T2125B #2 for income related to Business 2 and so on.

Re the numbering, I've been told that the numbers 1-4 in each category correspond to the numbered business or professional activity you have listed. So if you are self-employed and only have one business, choose T2125B #1. If you have multiple, T2125B #1 for income related to Business 1 and T2125B #2 for income related to Business 2 and so on.

The only thing I got from calling turbotax helpline  was a suggestion to buy "assist and review"  

@aj knight To check what industry code applies to you, please refer to this CRA guide: North American Industry Classification System (NAICS) Canada 2022 Version 1.0

That's honestly the type of conversation that I was expecting... low expectations going in only leaves room for me to be pleasantly surprised when I instead encounter a helpful attitude and accurate advice.

I have an amount reported in Box 48 of my T4A but I don't own a business (nor would I fall in the professional category).  Is there any alternative to filling out the T2125?

Having your own business is not necessary to earn this type of income, which is regarded as self-employment.

You must complete that section and select the one that applies to you in order to finish T2125.

If you are self-employed, you can report earned income and claim expenses when filling out T2125. Use the T2125 form to report either business or professional income and expenses.

T212B: Business income—income from any activity you do for a profit and includes sales, commissions, or fees. T2125P: Professional income—income that is from a profession that has a governing body (such as one for lawyers, professional engineers, etc.) T2125C: Commissions—income that is from commission sales.

You will select what applies best and suits your situation.

Thank you for choosing TurboTax.

Hello, I input T4A tips, do I need fill in the self-employment profile, too? I have a commission income box 20 as well as professional income box 48. When i filled the self-employment profile (I think it refers to  the T2125P and T2125C, respectively) , asked my income and I input the  number of box 20 and box 48 of my T4A forms, and my income becomes double! what should I do?  Only after i submit the form to CRA,  it indicate the gross income and I found the mistake. It was too late.  Before I submit, only the net income was showed and I thought it was correct since it looked lower than my total income, considering the expense.