Comverse ( CMVT), Ulticom ( ULCM) and Verint ( VRNT) got the boot from Nasdaq.

All three companies have been reviewing their stock option accounting amid a wide-ranging backdating scandal. As a result of the inquiries, the companies failed to file required financial reports with the Securities and Exchange Commission over the past year.

Nasdaq has informed the companies that they will be delisted Thursday. Starting Thursday, Comverse, Ulticom and Verint will trade on the pink sheets.

Nasdaq's decision seems to answer what has been a vexing question: How many quarters of delinquent filings does it take to get banished from a major stock exchange?

The answer, which could be germane to other late filers such as Juniper ( JNPR), seems to be four. Juniper, which hasn't filed data on its third and fourth quarters of 2006, promised Tuesday to file its overdue financial reports by the end of March.

As the backdating scandal widened, Comverse managed to attract a criminal investigation. Comverse CEO Kobi Alexander, ex-finance chief David Kreinberg and onetime senior general counsel William Sorin were charged in August with defrauding shareholders by backdating options in a bid to "evade the accounting, disclosure and tax consequences of granting in-the-money options."

Kreinberg pleaded guilty to conspiracy and securities fraud in October and agreed to cooperate with federal prosecutors. The next month, Sorin pleaded guilty to conspiracy to commit securities, mail and wire fraud. He faces a maximum of five years in prison at his sentencing in February. Alexander fled to Namibia and was arrested there in September. He faces an extradition hearing in April.

Comverse shares dropped 34 cents to $19.60, Ulticom was down 45 cents to $8.92, and Verint fell $1.44 to $32.88 in early trading Wednesday.