IRS NOTICE REFERENCE
Understanding your CP105 Notice
We made changes to your tax return because we found a miscalculation. As a result of these changes, you have a balance due.
General information only. Not legal or tax advice.
Notice details
- Notice code
- CP105
- Category
- Balance due and collection
- Severity tier
- Tier 2 — Action or response expected. The IRS has taken or proposed an action and expects a response or payment.
- Governing law
- §6303; §6321 (Internal Revenue Code sections)
- Source
- IRS.gov — Understanding Your IRS Notice
What this notice is
We made changes to your tax return because we found a miscalculation. As a result of these changes, you have a balance due.
Source: IRS.gov. Reproduced for reference. General information — not legal or tax advice.
What the IRS says to do
Read the notice carefully. Compare the figures on the notice with your tax return. Contact us within 10 days of the date of your notice if you disagree with the changes we made. Correct the copy of your tax return you kept for your records if you agree with our changes. Pay the amount you owe by the payment due date on the notice. Pay the amount you owe by the payment due date on the notice. Contact us to make payment arrangements if you can’t pay the amount you owe. Learn about payment options .
This is the IRS’s own guidance reproduced from the IRS notice page. It describes the IRS’s process — it is not legal or tax advice from TaxRiskOS.
Governing IRS procedure (Internal Revenue Manual)
The IRS’s own internal procedures for handling this notice type are documented in the Internal Revenue Manual:
- IRM 5.19.1 — 5.19.1 Balance Due
- IRM 5.19.4 — 5.19.4 Enforcement Action
- IRM 5.1.1 — 5.1.1 Miscellaneous Collection Procedures
Reference to published IRS procedure. General information — not legal or tax advice.
Official IRS reference
Read the official notice page on IRS.gov: https://www.irs.gov/individuals/understanding-your-cp105-notice
Related tools
TaxRiskOS is workflow software for practitioners — it captures the notice, computes the deadline, surfaces the escalation tier, and builds a document checklist. It documents process; it does not give advice or draft responses.
Check this notice’s deadline (free tool)