I am a member of two LLCs, and my K1s both indicate modest losses. Must I report these losses?

basically it is up to you;yes on your 1040. it is impossible to tell just from the K-1 whether you will owe taxes without knowing the rest of your information, you won't have to pay extra taxes on the K-1 loss ,in fact, it will probably lower your tax due. if this is considered a loss from a "passive activity" then you would need to have passive income in order to offset the loss. if you dont, then the loss will have 0 tax effect on your tax return and will be carried forward to future years.