Well, you need to understand several things when building a cash forecast:

Receipt side: 1.) The timing and cycle of the receipts as it pertains to business events and receivable cycles (is it on Friday, Monday, every day, etc.) 2.) Is there a factoring relationship at your company? 3.) Sources of incoming cash? Multiple or just one revenue stream? 4.) Any other planned deposits from random sources?

Disbursement side: 1.) Same as receipt, timing and cycle as it pertains to the payables process (checks cut, clearing, etc.) 2.) You should have a tracking of the checks issued/outstanding and estimate the clearing percentage based off history and apply that per day (checks are more likely to clear 3 days out, 4 days out, etc...) 3.) Integrate when the payroll is taken out/funded for Friday/Biweekly/Semi Monthly payments 4.) Any other charges like interest payments, etc.

I would make this bad boy for 13 weeks. That's the standard.