Letter 12C: Math or Clerical Error
Letter 12C is an IRS notice informing you of a math error, clerical mistake, or inconsistency on your tax return (such as addition/subtraction errors, incorrect entries, or mismatched data from forms like W-2s or 1099s). The IRS automatically corrects the issue and adjusts your refund, balance due, or credits accordingly.
Why It Matters: These errors can reduce your refund, create an unexpected balance, or delay processing—often without needing a full audit. Ignoring the letter may lead to penalties, interest, or collection actions if a balance is owed. If a simple fix has snowballed into IRS notices or tax debt, you’re not at fault for honest mistakes. Omni Tax Help reviews your Letter 12C, verifies the IRS changes, and helps file an amended return if needed to restore accuracy and resolve any fallout quickly.
Common Examples:
- Transposed numbers or wrong arithmetic.
- Missing or mismatched taxpayer ID info.
- Incorrectly claimed credits/deductions.
What to Do Next:
- Compare the IRS changes to your original return.
- Respond within 60 days if you disagree (include supporting docs).
- Pay any balance or claim your adjusted refund.