How do I know if I have to pay my tab bonus balance when I change my plan?

If you keep your current tab, you won't have to pay back the tab bonus. If you want to pay off the tab or get a new phone, you'd have to pay back the bonus, unless you got a special offer to waive the playback.

thanks for answering, Sophia! so my understanding is that as long as i keep the same $45/month plan, even if the data amount is different, i would not have to pay the tab balance bonus?

You can change your plan in selfserve. https://www.koodomobile.com/en/help/changing-your-rate-plan

As you are having a Tab, they only show you available plans that you could change while keeping the Tab (and Tab bonus). 

You can pay off your tab balance and not have to pay back the bonus.

Not necessarily. There are definitely circumstances where you need to pay it back, since the bonus is meant as an incentive to keep the tab for the entire duration.

I thought as long as you don't cancel or downgrade your plan you can pay your tab balance anytime 

I'm pretty sure that is not the case, but if someone has better knowledge than me in that regard, I'm sure I will be corrected 😊

Not true. Even if you are getting more data at the same plan rate as before, you are still making changes to your plan. The only exception is if they are keeping your base plan, while including some add-ons to your account. In any other instances, it will trigger the system and you will end up having to pay the remaining Tab balance and Tab Bonus balance. 

so if my understanding is correct, if i change to a plan that is shown in the Self Serve - change my plan, i will not pay any penalty, i will still keep the say Tab/Tab bonus balance?