Can you sue for back child support if there was no court order at that time?

No.

A few US states allow for the custodial parent to file for back support though the court, you are not sue but filing for support and it in some states can go back

A few US states allow for the custodial parent to file for back support though the court, you are not sue but filing for support and it in some states can go back

Even if there was no court order for support originally?

Even if there was no court order for support originally?

Yes, and one of the rules for it is evasion. If the NCP sought to evade child support then it may go back further then the filing date.

Generally support starts when the support is filed for. But, as noted, some areas do allow for awarding retroactive support. It will be up to the court and local law as to whether to allow it.

ANY question on law needs to include your general locale as laws vary by area.