OK, the B indicates a distribution from the designated Roth account in the plan. Offset distribution were made from both the traditional account and the designated Roth account to satisfy the loan. The code-1 Form 1099-R reports the distribution of the remaining balance from the traditional account. (Given that there is no code 1B Form 1099-R, it appears that the entire balance in the designated Roth account when to the offset distribution.
Each of these Forms 1099-R must be entered into TurboTax. If your husband does not come up with the necessary funds to complete rollovers of the code-MB and code-M1 distributions by the due date of his tax return, including extensions, the taxable amount shown in box 2a of each of these forms will add to AGI and taxable income. I'm guessing that the distribution of the remaining balance was more than 60 days ago and the deadline for rolling over of this portion has passed, so the amount in box 2a of the code-1 Form 1099-R will add to AGI and taxable income. There generally would have been mandatory tax withholding from the code-1 distribution, so the amount in box 4 of that Form 1099-R will be credited on Form 1040 line 25b, but from your statement that there the balance due on your tax return is $8,000, it seems that that the amount withheld was not sufficient to cover the increase in tax liability resulting from these distributions.
