Gross monthly income means your pay before taxes, social security and other deductions are made from your earnings. Make sure that you include part time job income and other earned and unearned income, including side jobs and “under the table” income, and regular money gifts from family or friends. If you (or your spouse) receive a check for the same amount of money each pay period, things are pretty simple in terms of calculating your income.
But if for example you work on commissions or work a different number of hours each pay period at an hourly rate, or get overtime occasionally, calculating income is more difficult (bonuses and commissions are considered income and should be factored into the income calculation, unless for example it was a one time bonus not likely to reoccur).
While sometimes it’s best to take an average from the last six months for example to calculate income, sometimes that just doesn’t work. (For example, if the previous six months of the year are the busiest time, and the next six months of the year are usually slow it’s not going to be accurate to use the pay info for the last six months.) The goal is to arrive at an accurate income figure which will likely re-occur going forward. There is no reason for example to use the average of the last six months if you just got a pay cut last week. (Or if the average was skewed by a one time bonus which isn’t likely to reoccur.)
So it may not be accurate to state that your last pay period income is representative of what your income really is. You should also note that if a party is unemployed and is capable of working and earning a certain amount, say $2,000.00 per month, then $2,000.00 per month should be “imputed” to that person (i.e., you should proceed as if that person’s income is $2,000.00 per month).
Similarly if a person is choosing to work at a job for less money than they are capable of earning, then you should impute the higher income figure to that person. If someone is self employed and it is difficult to determine what they make, especially if they under report their income, we can look at how much they spend each month without incurring any debt, in order to figure out their income.
Note that in calculating your monthly income, if you get paid biweekly, you should multiply your biweekly salary by 26, and then divide by 12. If you are paid weekly, do not multiply your weekly salary by 4 to get the monthly figure. Multiply the weekly by 52, and then divide by 12.