An average can be mathematically correct and still give a poor picture of the month in which an instalment must be paid. That matters when overtime, commission or family support changes through the year.
Separate the income by character
Begin with dependable contracted pay. List recurring but variable earnings separately, using enough months to show the range rather than selecting only the strongest period. Once-off sales, refunds and transfers between your own accounts are not earnings merely because they appear as credits.
Keep the timing visible
An annual commission paid in December cannot cover every monthly debit unless the household deliberately reserves it. State how the amount is managed and test the application using an ordinary month as well as an average month.
Explain support without assuming permanence
Where a relative contributes regularly, record the pattern and ask whether the commitment is documented and likely to continue for the finance term. A cautious application does not turn goodwill into guaranteed income.
The purpose is not to make variable work look weak. It is to prevent a strong average from concealing a fragile payment month.