What Is the Purpose of Form CT-1 X?

Use Form CT-1 X to correct errors on a previously filed Form CT-1. Use Form CT-1 X to correct:

• Tier 1 Employee tax, Tier 1 Employee Medicare tax, Tier 1 Employee Additional Medicare Tax, and Tier 2 Employee tax;

2 Instructions for Form CT-1 X (Rev. 4-2025)

• Tier 1 Employer tax, Tier 1 Employer Medicare tax, and Tier 2 Employer tax;

• Amounts reported on Form CT-1 for the credit for qualified sick and family leave compensation for leave taken after March 31, 2020, and before April 1, 2021, including adjustments to Form CT-1, lines 16, 23, 30, 31, 32, and 33;

• Amounts reported on Form CT-1 for the credit for qualified sick and family leave compensation for leave taken after March 31, 2021, and before October 1, 2021, including adjustments to Form CT-1, lines 17b, 24b, 36, 37, 38, 39, 40, and 41; and

• Amounts reported on Form CT-1 for the COBRA premium assistance credit, for periods of coverage beginning on or after April 1, 2021, through periods of coverage beginning on or before September 30, 2021, including adjustments to Form CT-1, lines 17c, 17d, and 24c.

Use Form 843, Claim for Refund and Request for Abatement, to request a refund or abatement of assessed interest or penalties. Don’t request a refund or abatement of assessed interest or penalties on Form CT-1 or Form CT-1 X.

We use the terms “correct” and “corrections” on

TIP Form CT-1 X and in these instructions to include

interest-free adjustments under sections 6205 and 6413 and claims for refund and abatement under sections 6402, 6414, and 6404. See Rev. Rul. 2009-39 for examples of how the interest-free adjustment and claim for refund rules apply in 10 different situations. You can find Rev. Rul. 2009-39, 2009-52 I.R.B. 951 at IRS.gov/irb/ 2009-52_IRB#RR-2009-39.

underreported tax amounts only and a second Form CT-1 X correcting the overreported tax amounts.

You’ll use the adjustment process if you underreported RRTA taxes and are making a payment, or if you overreported RRTA taxes and will be applying the credit to Form CT-1 for the period during which you file Form CT-1 X. However, see the Caution under Is There a Deadline for Filing Form CT-1 X, later, if you’re correcting overreported tax amounts during the last 90 days of a period of limitations. You’ll use the claim process if you overreported RRTA taxes and are requesting a refund or abatement of the overreported tax amount. Follow the chart on page 6 of Form CT-1 X for help in choosing whether to use the adjustment process or the claim process. Be sure to provide a detailed explanation on line 43 for each correction that you show on Form CT-1 X.

Continue to report current year adjustments on Form CT-1, line 14.

You have additional requirements to complete when filing Form CT-1 X, such as certifying that you filed (or will file) all applicable Forms W-2, Wage and Tax Statement, and Forms W-2c, Corrected Wage and Tax Statement, with the Social Security Administration (SSA). For corrections of overreported Tier 1 and Tier 2 taxes, you must make any certifications that apply to your situation.

Be sure to give us a detailed explanation on line 43 for each correction you show on Form CT-1 X.

Don’t use Form CT-1 X to correct Form 941,