You only submit documents for your financial year. You don't need to cover the time from the end of the financial year and application date.
Was the TAXABLE income for your financial year over $18,600? That's the key part. You need to have paid taxes on the required amount.
Alternatively, does your wife work? Does her income meet the requirement? If so, you can bypass your income and just use her's if she is employed by a company.