Maryland taxing my fulltime student child because I can claim as a dependent?

[Gimel]

We used TurboTax to file my full-time student child's taxes on a $15K income university job in Maryland in which the feds withheld $235 -- and are refunding $171 -- and Maryland withheld $707 -- was refunding a couple hundred. Alas, his returns were rejected because he hadn't checked the box that said he could be claimed as a dependent. When we did, the Feds were still refunding $171 but Maryland now is saying he OWES another $271 -- for a grand total of $980 of 6.5% on $15K? Can that really be right? Are there credits or deductions we should be looking for to offset that in Maryland? I'm seeing Maryland's top tax rate is less than 6% and he's paying over that on $15K???

Appreciate any advice in advance

[LeticiaF1]

There's probably something incorrect with his state return.  He should be getting a refund, not a balance based on the information you provided.  TurboTax transfers data from your federal return to your state return. Before you start fixing your state return, look at your federal return again. Make sure everything is correct, including his W2 forms.

After you review your federal return, select the State Taxes tab and review the state section. Pay close attention to the information, especially if you have made changes to your federal return. There might be new sections that need to be completed. 

Troubleshooting common federal to state transfer issues