I haven’t done it, but here is what Schwab has in their FAQ [1]:
> While we can't guarantee there will be a market for it, we'll help you sell the CD at the current market rate by requesting bids on your CD and contacting you with the highest one. If you decide to sell, you'll receive the bid price plus any accrued interest. There are no guarantees that you'll get what you originally paid for the CD.
> While we can't guarantee there will be a market for it, we'll help you sell the CD at the current market rate by requesting bids on your CD and contacting you with the highest one. If you decide to sell, you'll receive the bid price plus any accrued interest. There are no guarantees that you'll get what you originally paid for the CD.
[1] https://www.schwab.com/fixed-income/certificates-deposit