Mathew Knowles -- Here's a Switch ... Screw Your Accountant!

Mathew Knowles has a knack for finding financial trouble ... he just got socked with a big judgment by a company he hired to get him out of the money hole he dug for himself.

Check this out ... Beyonce's dad hired Platinum Tax Defenders to deal with Uncle Sam, who was all over his ass.

But Platinum doesn't come cheap ... charging more than $62,000 for 100 hours of work. Mr. Knowles paid a skosh over $37,000 and that's all she wrote ... so claims the tax company.

So, Platinum sued and Knowles was a no-show in court, so he got socked with a judgment north of $20k.

Despite the judgement, an attorney for Knowles tells us he still vehemently denies the allegations in the complaint.