Balance Sheet will not Balance

Please do not do this.

First of all, if your associate or analyst checking the model is using any form of dependency or tracer add-in for Excel, you'll be busted in about 4 seconds, which will make you look like both a fool and a liar. It's much better that you ask for help on how to fix your mistake than to present something that you know is incorrect and get busted for it.  

Second, if your balance sheet is not balancing for the forecasting years, you've made a mistake somewhere. That's okay, but you need to figure out where it is and check your numbers again until you find it. My best advice would be to check the following items, which is where I've seen a lot of people go wrong: 

- You have used the wrong +/- in front of any net working capital item, such as AR, AP, Inventory. (Most common)

- There's a mistake in your cash balance (excess cash not being transferred to cash or equity account). 

- You have counted taxes double, ie, used Net earnings and removed taxes again in your cash flow statement. 

- Your depreciation on forecast CAPEX is calculated incorrectly, or you have double-counted depreciation. 

- You have not included other short term debt (could be a revolver) into your debt account in the balance sheet.

Other things that could be wrong; If you are forecasting large investments, take up new debt in the forecasting period etc. try to remove these completely while you figure out your mistake, or set them to 0, before adding them back again. This way you can "check" things off as you go through your model, obviously depending on how complicated it is, but if it's a simple pitch valuation, this should be feasible.