I’ve paid off half of what I owe the IRS, when will I get notified to pay off the rest of it?

The sooner you pay, the less interest you will be subject to.  Why are you waiting to be notified of the amount or a date?   If you are unsure how much you still owe, you can check your online account with the IRS.  You can pay directly on the IRS site.

 

https://www.irs.gov/payments/your-online-account

 

https://www.irs.gov/payments

 

 

https://ttlc.intuit.com/community/tax-payments/help/how-can-i-pay-my-federal-taxes/00/26212

 

 

https://ttlc.intuit.com/community/tax-payments/help/how-do-i-pay-my-irs-tax-due-with-a-check-or-money-order/00/26403