We have a custom script that we use to update non-G/L impacting custom fields on transactions after a period is closed. It's been working for nearly 2 years without issue. Lately, we're running into errors saying "The G/L impact of a transaction in a closed period cannot be changed." In the past when we've run into this, it was an issue with updated global account mappings and I was able to track it down. This time, I can't figure out what G/L impact changes are supposedly happening. When I try manually editing the transaction (to avoid the script), I get the same error. Is there any way to figure out what G/L changes it's trying to make? I've checked everything I can think of and nothing obvious is standing out. NetSuite support has been less-than-helpful.

Did you check allow non-gl changes when closing the period?

Tax can cause this issue