Advanced collection write off scenario

I have this business scenario, if customer not paid then after certain days they doing the AR write off for the invoice. Even though they are doing write off they wanted to consider that customer as a delinquent customer and in collection they still want to keep that customer as a delinquent. I can alter scoring engine logic to make that customer as delinquent but in future customer pay back the amount , how can we revert the write off and make the customer as active?

Can you suggest the approach for this scenario