The following article could be helpful to you:
http://www.schumanlaw.ca/blog/how-far-back-in-the-past.html

   

Have fun with that one! If nothing was written legally...and even if it was WRITTEN LEGALLY fro does what the want! Always has always will! I have a legally written document, both myself and ex wife and lawyers signed off on, and durring this covid crap FRO is garnishing my wages! No payments have been missed and any outstanding is paid back, but still loke normal FRO does what they want! They are above the law apparently! I also heard if the kid is 18 you and you ex need to file, and make sure you follow up, but FRO has a nasty habbit of not listening and not closing the file off, and then it's your fault there too, when they come after you for non payment, even though both sides have closed the file off! Hood luck with everything! BEWARE OF FRO

   

3 years back. But if you can prove that you agreed to something else. Like making the payments you have for so long. Speak to a mediator about closing your order with her. That way you have proof your trying to finalize everything. That way if she hits you with proceedings you can say she's trying to extend proceeding with unnecessary costs for backdated support that you agreed on in the past to an offset amount.