Is the client a part year resident in each state?   or did they go to Missouri just to work but live in Iowa?

they did the work from their home in Iowa-the business that reported the 1099 is in Missouri & entered Missouri in box 17  &  state income in box 18

thank you.  Of course they can- I don't know what I was thinking. I never saw anything in the box 17/18 before & it threw me .   Thank youagain

how do I recommend to show appreciation?

I converted to an answer....Ive seen a few 1099MISC with state info on them...they don't usually have that though.

@Just £isa Now! I've got a last minute one:  Client (MO resident) is a football referee at the university level.  He has one 1099 from a third party "middle man" covering work for several universities.  This year, for the first time, there was CA tax withheld on part of the income.  Box 17 shows CA/   , with no entry for the state payer number.  Middle man claims it's not their problem (translation "I don't know and don't want to spend the time to research this.")  Any ideas?  Thanks, Jay  

Were state taxes actually taken out of the pay?   The payer cant pay the CA state taxes in without a CA state ID number, so if they were actually withheld, where did the money go?

The 1099 shows state tax withheld in box 16 and CA wages in box 18.  At this point, I'm going to have the client call each school he worked for in CA and see if he can find out which one withheld and get their state number.  That's the only thing I can think of.  Thanks for taking the time to think about it.

Correction to above:  not wages in box 18, but self-employed money received.

If he was IN California working then yes, he may have a CA filing requirement, but you also need a CA state ID number or he wont get those withholdings applied his return.