is this a 1099-OID from Schwab by chance? Box 10 on 1099-OID doesn't work for Munis in TT and I think Schwab clubs reports bond premium (that would otherwise be on 1099-INT) into 1099-OID on certain bonds if they have OID also. If using desktop you can enter it fine on EasyStep but in Forms mode it flags an error and doesn't like anything above zero.
Got stuck on this a few yeas ago, since then I just put zero for Box 10 and put that amount in as an "other" adjustment (not the other 'bond premium' adjustment categories, or it complains about Box 10 again).
For me the bulk of Box 11 is due to a few zero coupon munis, technically at individual bond level which have the Box 10 there isn't enough income for the premium adjustment because it's on 1099-INT. But it doesn't matter for me in the aggregate. If your Box 10 is bigger than your Box 11 you may still get an error with this approach, in which case I would put the adjustment on 1099-INT. Presumably these are small amounts and won't affect Fed taxes (assuming no AMT), just State.
Here's a long old thread on this topic
https://ttlc.intuit.com/community/taxes/discussion/1099-oid-bond-premium-on-tax-free/00/2006280
Not a CPA/Expert just my 2 cents on this topic
