assert a deficiency

16:16 Mar 9, 2019 

A deficiency is what remains of a debt after the creditor has taken the collateral (or the deposit, if applicable).
https://www.investopedia.com/terms/d/deficiency-balance.asp

So this isn't just a solde impayé. It's more specific than that. I don't know if financial or legal French has a specific term for "debt remaining after the collateral is sold," but either a specific term or a translation that means that would be appropriate here. Anne's proposed "solde impayé" is close, but broader than "deficiency" and thus potentially misleading.

21:00 Mar 8, 2019 

C'est la partie d'un impayé qui ne peut pas être remboursée après la vente des collatéraux ou des biens qui ont été repris. Cf. <p>After crediting the sale proceeds and debiting the costs associated with the vehicle’s
repossession and liquidation, Americredit filed an amended proof of claim for the deficiency in an amount of $9,445.73. (https://www.govinfo.gov/content/pkg/USCOURTS-pamb-1_06-bk-00... ou <p>If you fail to make car, van, truck, motorcycle, or other auto payments, your car loan lender will likely repossess your motor vehicle. If that happens, your lender can sell your car and use the proceeds of the sale to recover what you still owe to them. If the sale proceeds don’t cover the entire amount you owe, the car lender may be able to go after you for the remaining amount, called the deficiency. (https://www.thebankruptcysite.org/resources/defenses-deficie...