Filed 1065 instead of 100S

[khorshed]

in 2018 a new client came to me & asked to file 2017 LLC taxes, he mentioned that the LLC was converted to S Corp in 2018. I went ahead & filed 2017 Form 1065 Fed & Form 568 State of Ca. Recently, he received a letter that he must file form 100s for 2017 as it turns out that the LLC was converted to S Corp in Dec 2017. My question what's the best solution. Should I amend 2017 forms (1065 & 568) and refile them with $0, amend all partners K1 and try to get refund for any taxes paid for the LLC? or should I file 2017 Form 100s with $0 which will be a lot easier?  

[Just-Lisa-Now-]

So was it a partnership for the rest of the 2017 year until Dec when it became an SCorp?

[khorshed]

yes

[qbteachmt]

Did they do some sort of year end 2017 payroll, or skip that detail?

[khorshed]

They had payroll as LLC & as S Corp !!!