Deposit it through an ATM.  They'll take anything.  

Was this an e-filed return?   The client didn't want a direct deposit?  (Probably doesn't want a vaccination, either.)  

My name gets misspelled all the time. I just sign the back both ways.

Yes, It was misspelled on the tax return as well.  

It's easier to get a hold of Biden than the local IRS office...

yes, this was filed as an e-file return.  They are more comfortable in receiving checks I guess. Ok, so their last name was totally wrong on the tax return and on the paper check.  Are you sure this will not affect the deposit at an ATM when the check is being cleared?

"Yes, It was misspelled on the tax return as well."

The check can be deposited. The rest can be fixed separately.

https://ttlc.intuit.com/community/taxes/discussion/i-didn-t-notice-that-my-name-was-misspelled-on-my...

https://www.reddit.com/r/personalfinance/comments/3vgdrc/irs_spelled_my_name_wrong_on_refund_check/

Just to comment that you posted while I was replying. This is a bit different: "Ok, so their last name was totally wrong on the tax return and on the paper check."

What matters is the significance. Gomes or Gomez is the not the same as Smith vs Gomez. I don't know what "totally wrong" means.

Sorry I miscommunicated. Their last name is actually Guardado and I mistakenly put "Gallardo".

I'm surprised the IRS didn't reject that as a mismatch, then.

I agree, this should have been rejected....are these new clients? Did you see their IDs and SS cards? Something seems fishy here.

Well, if you can run it through the ATM machine or online banking you’ll probably have to amend the tax return and then  request re-issuance. It’s a fairly ugly process and will likely take a few months. 

https://sa.www4.irs.gov/irfof/lang/en/irtrconlinehelp.jsp

The "name check" I usually see is just the first four letters of the last name.  If IRS sees Schm, they don't look farther for Schmid or Schmuck.  But maybe that has changed.  

ATM's don't look at names on checks.  When clients ask me how to make out their check, I tell them they can write "Osama bin Laden" for all the bank cares.  I have a rubber stamp for deposits to my business account; I don't sign anything.  Last month a client had a small health-insurance refund check payable to his wife, who died two years ago.  He was uncomfortable taking it to his bank, so I cashed it for him.