Why it is different
When you are on a traditional paycheck, your income is already a number on a document someone else produced. When you are self-employed, your income has to be established from your business records — typically tax returns and supporting documentation.
That means the picture a lender sees is the one your tax returns paint. If you have been deducting aggressively, the number on your return may be lower than what you actually take home. That is a legal and often sensible choice — but it is worth knowing it affects what your file can support.