A child support payor may bring a motion to vary the payment of a temporary support order made retroactively, however, such orders are an exception and not the rule. Strong evidence is needed to establish why the support order shall be varied. The case of Tran v. Tran (2015 ONSC 5838 CanLII) demonstrates the uphill battle that is in place for a payor and also shows how anything less than compelling undisputed evidence will be insufficient for fulfilling the task.
In Tran v. Tran, the courts did not grant the order that the payor was seeking as there was evidence lacking on the following grounds:
1) payor was fired from his job;
2) payor could not pay child support because FRO would not accept payments;
3) payor was able to maintain himself on his limited salary (considering his income and expenses as disclosed on his financial statement);
4) payor was not intentionally underemployed;
5) payor did not have any other source of income; and
6) payor’s income as ascertained through basic disclosure.
 http://www.canlii.org/en/on/onsc/doc/2015/2015onsc5838/2015onsc5838.html