Sometimes, a donor pledges a certain amount but for whatever reason (personal, third-party fees, etc.) the full donation is not received. Currently, you can only write off the entire pledge. But if, say, $300 remains outstanding on a $2,000 pledge, there is no straightforward way to indicate that the dollars are not going to come in. Instead, it remains indefinitely in arrears unless the pledge is deleted, re-entered as two, and the amount that is not going to be collected is written off.
When a pledge is written off, we only write off the remaining balance so you can write off the remaining $300 in the scenario above.
https://kb.blackbaud.com/knowledgebase/articles/Article/105408