Determining your guideline income starts with a review of your most recent income tax return. The key section you'll need to locate is "Step Two: Total Income," which appears a few pages into your return and reports all income sources from the previous year.

When using a support calculator, you can go through each entry on your tax return, and add them into the calculator. You can add in each income source by searching out the income tax line number and enter the number in that way.

For each income line item, ask yourself whether the previous year's figure provides an accurate estimate of your current year's expected earnings. If the number remains relevant to your current situation, use it as-is. However, if your income has changed, you'll need to make better educated guess at a more appropriate number.

Say, for example, your employment income line is 10,100, and that number has now changed a bit. You can look at your most recent pay cheques or average your last three pay cheques to figure out what your gross income per cheque is and then multiply that by the number of pay periods you have in a year. So 24 pay periods if you get paid twice per month and 26 pay periods if you're paid bi-weekly.

If you have a new job offer specifying your new salary, use the figure outlined in your employment letter. Just continue along with the pattern that you're already following. You don't have to commit to income that you're not earning, but if you're earning it now and there's no change imminently expected, then include it.

Put in your best estimate by including income sources that you're currently earning and expect to continue receiving without imminent changes. While it can feel uncomfortable committing to income that doesn't feel completely guaranteed, remember that support calculations can and should be recalculated if circumstances change significantly.

Consider whether you've acquired new income sources since your last tax filing. Examples could include:

Conversely, you may need to remove income sources that are no longer relevant. For example, if your tax return showed rental income but you're now selling the property, it would be reasonable to exclude future rental income from your calculations.

Your guideline income for determining child support and spousal support specifically excludes:

These exclusions ensure that support calculations focus on your actual earning capacity rather than government benefits or support already received.

After determining your basic income sources, review the miscellaneous adjustments section to identify any items that may apply to you. You can consult step two, miscellaneous adjustments below for a listing of all the items that can be added back or deducted from your income. At that point, there may be a few circumstances that require special considerations.

Maintain thorough documentation of your income to make it easy for recalculation when necessary. For example, keep track of the following:

Once you've accurately determined your guideline income, you can proceed with confidence knowing that your support calculations are based on correct and current financial information, ensuring that resulting support arrangements reflect your actual financial capacity and create sustainable agreements for both parties.

Remember that income determination is an ongoing process rather than a one-time calculation, with regular updates required as circumstances change throughout your separation and after your divorce.