Financial Obligations before an agreement is reached?

You have no “legal obligation” until there is an order or agreement in place. The court will consider a retroactive award of support (child or spousal) if it can be shown that your ex made demands for support or for financial disclosure and that you delayed providing the info or delayed paying – in which case the court may order guideline support retroactive to the date of the demand. As it is inevitable (given the significant disparity in your incomes) that you will ultimately be ordered to pay both spousal and child support to your ex, you would be better served by paying at least the child support set off amount under the guidelines even in the absence of an agreement. However in order for any spousal support to be tax deductible to you (and taxable to her), you must have a written agreement or court order in place. Therefore you may wish to await a formal agreement or order before paying spousal support in order to attain the tax deductibility of those payments.