In In re Marriage of Gruen (2011) 191 Cal.App.4th 627 the husband filed a petition for dissolution of the marriage and an order to show cause (OSC) regarding child and spousal support and other matters. (Gruen, supra, 191 Cal.App.4th at p. 632.) The court held a hearing on the OSC and ordered the husband to pay the wife $40,000 per month in temporary support, stating the order was made " 'on an interim, without prejudice basis, pending the next hearing.' " (Id. at p. 633.) The court also appointed an expert to assist it in determining the husband's income available for support. The court continued the hearing on the husband's OSC, and on the continued hearing date, the husband asked the court to take the matter off calendar insofar as it pertained to support and to continue the initial support order pending preparation of the expert's report. About six months later, the husband filed a motion for " 'retroactive reimbursement' " seeking a reduction in his support obligation retroactive to the date of the court's initial temporary support order. (Id. at pp. 633-635.) Based on the appointed expert's final report on the husband's income, the court ordered the husband to pay monthly support in varying amounts that were less than the initial $40,000 award for three different time periods, the earliest of which began on the date of the initial support order. (Id. at p. 634.) At a later hearing the court further reduced the awards going back to the date of the initial award. (Id. at p. 636.) This court reversed the Gruen trial court's orders retroactively modifying its initial temporary support order, concluding that a trial court lacks jurisdiction to retroactively modify a temporary support order to any date earlier than the date of the filing of a notice of motion or OSC to modify the order. (Gruen, supra, 191 Cal.App.4th at pp. 631, 638.) That conclusion is based primarily on section 3603, which provides that a temporary or pendente lite support order " 'may be modified or terminated at any time except as to an amount that accrued before the date of the filing of the notice of motion or order to show cause to modify or terminate.' " (Id. at p. 638; see also 3651, subd. (c) permanent support orders.) The Court concluded that the trial court had erred in retroactively modifying a pendente lite child and spousal support order. In that case, a husband filed for dissolution of his marriage and applied for an order to show cause (OSC) concerning child and spousal support, among other matters. (Id. at p. 632.) On August 1, 2008, the trial court entered an order directing the husband to pay his wife $40,000 per month in temporary support. Also on August 1, the court appointed an expert to assist the court "in determining husband's income available for support." (Id. at p. 633.) On August 21, the husband asked the court to take his OSC off calendar insofar as it pertained to support. (Ibid.) In February 2009, the husband filed a motion for "retroactive reimbursement," in which he sought a "reduction in his support obligation, retroactive to August 1, 2008," based on the expert's draft report concerning his income. (Id. at pp. 633-634.) In June 2009, the trial court considered the expert's final report and retroactively reduced the temporary support award, effective August 1, 2008. (Id. at pp. 635-636.) In concluding that the trial court had erred in retroactively modifying its August 1, 2008 order, the Gruen court noted that the August 1 order was "final" and "immediately operative and directly appealable." (Gruen, supra, 191 Cal.App.4th at p. 639.) The Gruen court further stated that the trial court was mistaken in thinking that it could "retroactively modify a temporary order." (Ibid.) The Gruen court also concluded that even prospective modification of the order was improper under the circumstances of that case, stating, "Even to the extent the modifications of the August 1, 2008 order were prospective, they exceeded the court's jurisdiction since they were not based on any pending motion or OSC for modification." (Gruen, supra, 191 Cal.App.4th at p. 640.) In reaching this conclusion, the Gruen court noted that the husband had taken his original OSC off calendar and had never filed a motion to modify the August 1 support order. (Id. at pp. 640-641.)