[Rules] Assault on dug in units

[plloyd1010]

According to the rules Attacking units in assault should get a negative modifier against defending units in dug in status.
Negative column modifiers for dug-in units (16.2) only benefit defending units which are actually dug in.
But I see no such modifier on the assault sheet. Is this correct?

That is correct. There is no defensive modifier for being dug in vs. assault. All defensive modifiers apply to direct, AT and bombardment fire. The advantage to being dug in, in assault is that the defender may take first fire using the dug in units.