Time sheet Database design with multiple clients
There is no perfect answer for this only you can decide the best option. And it has a lot to do with tradeoffs, and preferences. How much time you have now vs maintenance in the future.

You could have:


1 table for all customers.
A table(s) for each customer
A database for each customer.


Option 1 is ideal if you hope to reuse and resell to many customers. The downside is that you cant use the db schema to enforce rules per column unless the rule applies to all customers. Which makes enforcing business rules difficult. 

Option 2 allows you to use the schema to enforce rules per customer. But the queries and app design become more complex. 

Option 3 means you can create a customised solution per customer, but it will require more effort to maintain. 

Start by modelling the requirements and see how much commonality there is and what is or is not mandatory. 

Understanding business rules and things like one to many relationships will be key to getting it right. 

If you dont expect the db to enforce mandatory fields and can handle that in the application personally i would lean towards option 1 with as much re-use as possible.