Is it possible to request the courts in NJ to backdate a reduction in child support? Due to an error on my behalf I was forced out of the United States for 3 years while I was correcting my immigration status. During this time I earned less than half of what I was while living and working in NJ.
I never filed at the time of my departure as I was out of the country but have made payments as best I can since being in the UK.
Can the court backdate the reduction and amend the arrears?

No. It was your responsibiity to report any changes in income when they occurred. If you were forced out of the US you should have retained an Attorney to address this issue. You did not have to be in the Country.