This is why it's not the same as this UI topic: "My original question was about Supplemental Unemployment Benefits (SUB pay) being repaid to an employer who included the original payment of (SUB) as taxable income on a W-2 for 2020."

A SUB is an employer-sponsored plan, and some States require submission and approval, and the employer might have a 501(c)(17) trust for this.

https://www.irs.gov/charities-non-profits/other-non-profits/supplemental-unemployment-benefits-trust...

As far as "taxable income:" A SUB payment is not typically subject to FICA, but is subject to income taxes. That's what makes a SUB different than Severance pay, too. And it should not impact UI eligibility.

The IRS has resources for all of this.

https://www.irs.gov/pub/irs-pdf/p525.pdf

"Supplemental unemployment benefits.Benefits received from an employer-financed fund (to which the employees didn't contribute) aren't unemployment compensation. They're taxable as wages and are subject to withholding for income tax. They may be subject to social security and Medicare taxes. For more information, see Supplemental Unemployment Benefits in section 5 of Pub. 15-A. Report these payments on line 1 of Form 1040 or 1040-SR.

And:

"Repaid wages subject to social security and Medicare taxes.

If you had to repay an amount that you included in your wages or compensation in an earlier year on which social security, Medicare, or tier 1 RRTA taxes were paid, ask your employer to refund the excess amount to you. If the employer refuses to refund the taxes, ask for a statement indicating the amount of the overcollection to support your claim. File a claim for refund using Form 843."