IRS notices don’t exist in isolation. They are part of an interconnected system. Understanding these relationships helps you anticipate what’s coming next and prepare accordingly.
The Collection Sequence
The primary collection path follows this order:
CP14 → CP501 → CP503 → CP504 → LT11 (Letter 1058) → Active Levy
Each notice in this chain escalates both the urgency and the IRS’s enforcement authority. You can stop the escalation at any point by entering into a resolution — such as an installment agreement, an offer in compromise, or requesting Currently Not Collectible status.
The Audit Path
If you’re being audited, the sequence typically looks like this:
Audit Letter (e.g., Letter 566 or Letter 2205) → 30-Day Letter (Letter 525 or Letter 950) → Notice of Deficiency (90-Day Letter) → CP14 (if balance due) → Collection Sequence
An audit doesn’t necessarily mean you’ll owe more tax. But if the IRS determines a deficiency, the resulting balance enters the collection sequence above.
The Unfiled Return Path
CP59 → CP515 → CP518 → CP2566 (Substitute for Return) → CP14 → Collection Sequence
If you haven’t filed a required return, the IRS will eventually file one for you — called a Substitute for Return (SFR). SFRs are almost always unfavorable because the IRS uses single or married-filing-separately status and might not give you credit for deductions and credits you’re entitled to.