shokujishimashita / shokuji o shimashita
 

My question is quite simple: Are しょくじ を します (shokuji wo shimasu) and しょくじします (shokujishimasu) just the same? If so, which one do you normal use and why? I also think it's the same for all verbs with Noun+shimasu, are they always like this?

I think "しょくじをします:SHOKUJI WO SHI-MASU;I will have meal" is the right form. and " しょくじします:SHOKUJI SHI-MARU;I will have meal" is just having "を：WO" omitted and sounds rude.

"しょくじします:SHOKUJI SHI-MASU" is also recognized as "noun+SHIMASU" but when "WO" could be added, it sounds like rough or rude talking.

Thank you RadioKid.
So without "wo" does it really sound rude or just a bit informal?

Not so rude. Japanese people often use "noun+SURU" in casual written messages.

Actually, it is no problem for foreigners to use "noun + SHIMARU".