Hi jacqui71,

Checking the ATO website here for current outages, it seemed they had a weekly system outage for maintenance yesterday between 11:30pm AEST and ending today at 7:00am AEST. Outages of this kind can generate this application error whilst the ATO's systems are down, so I would encourage you to try later this morning to see if you get the same BAS lodgement error. That being said, if you try and still receive the same error there are a couple things we would ask you to check and follow to troubleshoot the error.

Firstly, it could be a simple browser error that is generating a application error even when all connections are set up correctly. I would advise to check our browser troubleshooting guide here which includes clearing cache and cookies, whilst also trying different web browsers e.g. Firefox or Chrome to try submit the BAS through QuickBooks again. 

Secondly, you mentioned you are currently registered to lodge with ATO via Electronic Lodgment and Exactor. I would kindly ask you reach out to our friendly support staff by clicking here so we can confirm the ATO connection is active, and troubleshoot further. 

Hope to hear this gets resolved, 

-Steven