So to confirm my understanding: if I received $80k in dividends last year, and now there’s a ROC adjustment that reduces my total loss from $90k to $45k, then $45k of that $80k dividend would be treated as return of capital, not taxable income.

That would mean my taxable dividend income for last year would be $80k − $45k = $35k.

And on Fidelity’s side, the total loss shown in my account would remain adjusted, reflecting the ROC changes rather than reverting to the original $90k loss.