Before the 15th day of the 4th month after the end of the tax year – single owner LLC – 1040 NR form
By the 15th day of the 3rd month after the end of the tax year – LLC partnership (two or more owners) – 1065 form
By the 15th day of the 4th month after the end of the tax year of the LLC partnership (two or more owners) – each of the owners shows his part of the profits in his personal 1040 NR declaration and submits it.
Before the 15th day of the 4th month after the end of the tax year – C-corporation – 1120 form