If you don't file a tax return when required, you are asking for trouble

DE routinely reconstructs tax returns for residents who are extremely delinquent and who have ignored repeated requests to file returns. They can use the income amounts reported to them by payees; bank statements, credit card statements, cancelled checks, customer bills and cash receipts; other methods (such as income earned in other years) to estimate income and the related taxes and these assessments are binding. The courts found it legal for them to disregard adjustments proposed  by the taxpayer after the assessments were made based on reconstruction. If the taxpayers had their own numbers, they should have filed a return to begin with. The state really ought to charge them fees for the accounting work as well!