The number of letters sent out under Centrelink's controversial robo-debt policy has soared past 230,000 as the federal appeals tribunal braces for a flood of disputes.

Treasury costings have put the price of Centrelink's data-matching and debt recovery at least $93 million, including payments to commercial debt collectors.

Pluto is not a dog, says Department of Human Services spokesman Hank Jongen.

The election policy costings, from mid-2016 also predict the cash-strapped Administrative Appeals Tribunal will have to find more than $3 million to cope with the expected flood of Centrelink clients taking legal action to fight against debts claimed by the welfare agency.

But there is good news for the millions of Australian families who receive family tax benefits; they are not on Centrelink's debt recovery hit list.