I have filed joint 130/485 for my Mom last monday. Now one week later, I found I forgot to attached AP (131 form) with it, which is free of charge if filed together with 130/485. My question is can I file this form now with no fee attached.
-Yes, your mother can apply for the AP any time without fee after she gets the I-485 receipt.
Is there any chance that this will be accepted without the fee.
-AP and EAD application is free based on pending I-485 like your mother's case no matter when you apply for it.
Could I attach a letter to explain it?
-No. Just provide the copy of the I-485 receipt.