Penalty calculations, which do not correlate with profits, present insufficient financial disincentives for businesses to collude.

Craig Willett, an accountant in Provo, Utah, plans to file his own return without the estimated tax penalty calculations and let the I.R.S. take a whack at it.

Often the I.R.S. proposes a larger penalty than is required under the complex rules on timing of payments, said Tom Persky, a former I.R.S. executive who designed TimeValue's penalty calculation software.