“This Is How We Do It” singer Montell Jordan insists he’s no deadbeat taxpayer — telling TMZ, he’s already paid his $617,000 tax bill … the money just hasn’t made its way into the pockets of the IRS … yet.

TMZ broke the story — the IRS filed a Federal Tax Lien against Jordan recently, claiming the singer still owes $617,987.06 in back taxes from 1999-2001.

But it’s not so cut and dry — Montell tells us, he paid the debt years ago by selling his music catalog … but the money’s been sitting frozen in an account administered by the U.S. Trustee Program, a division of the Department of Justice that oversees bankruptcy cases.

Montell filed for bankruptcy in 2004 — and says he’s still disputing some of the IRS penalties he’s incurred. He expects the money to be released to the IRS in a few weeks when he settles negotiations over the penalties … at which point the case will be closed.