I need to design a database with the following requirements:

For each Contract, there can be 1->many Projects
For each Project, there can be 0->many sub-Projects
For each sub-Project, there can be 0->many subsub-Projects
For each subsub-Project, there can be 0->many subsubsub-Projects
For each subsubsub-Project, there can be 0->many subsubsubsub-Projects
....(there can be up to 7 levels of Projects...
For each subsubsubsubsubsubsubsub-Project, there can be 0-many Tasks

I hate to create 7 (identical) Projects tables, especially since there will seldom be more than 3 levels of nesting. However, there will often be data at the lowest level (Task).

Any ideas? I hope this makes sense

for your sub-sub-sub-... structure, see this article: Categories and Subcategories