When I calculate “internal rate of return (IRR)”, should I include cash balance?
Both are correct depending on what you are really trying to evaluate. If you only want to understand how that particular investment you were taking money in and out of did by itself than you would ignore the cash.  You might use this if you were thinking of replacing that particular investment with another but keeping the in/out strategy. If you want to understand how the whole investment strategy worked (both the in/out motion and the choice of investment) than you would definitely want to include the cash component as that is necessary for the strategy and would be your final return if you implemented that strategy. As a side note, neither IRR or CAGR are not great ways to judge investment strategies as they have some odd timing issues and they don't take into account risk.
Regardless of how long the mortgage has left, the return you get on prepayments is identical to the mortgage rate. (What happens on your tax return is a different matter.) It's easier to get a decent financial calculator (The TI BA-35 is my favorite) than to construct spreadsheets which may or may not contain equation errors. When I duplicate John's numbers, $100K mortgage, 4% rate, I get a 60 mo remaining balance of 90,447.51 and with $50 extra, $87132.56, a diff of $3314.95. $314.95 return on the $3000. $315 over 5yrs is $63/yr, over an average $1500 put in, 63/1500 = 4.2%.  Of course the simple math of just averaging the payment creates that .2% error. A 60 payment $50 returning $314.95 produces 4.000%. @Peter K - with all due respect, there's nothing for me about time value of money calculations that can be counter-intuitive. While I like playing with spreadsheets, the first thing I do is run a few scenarios and double check using the calculator. Your updated sheet is now at 3.76%? A time vaule of money calculation should not have rounding errors that larger. It's larger than my back of envelope calculation.  @Kaushik - if you don't need the money, and would buy a CD at the rate of your mortgage, then pay early. Nothing wrong with that. "Re. question 2 If I buy 20 shares every year, how do I get proper IRR? ... (I would   have multiple purchase dates) Use the money-weighted return calculation: http://en.wikipedia.org/wiki/Rate_of_return#Internal_rate_of_return  where t is the fraction of the time period and Ct is the cash flow at that time period. For the treatment of dividends, if they are reinvested then there should not be an external cash flow for the dividend.  They are included in the final value and the return is termed ""total return"".  If the dividends are taken in cash, the return based on the final value is ""net return"". The money-weighted return for question 2, with reinvested dividends, can be found by solving for r, the rate for the whole 431 day period, in the NPV summation. Now annualising And in Excel" Should I use the profit to pay down student loans or just roll it into my next house in order to have a lower mortgage amount? Calculate the amount of interest in each scenario, where the two scenarios are: Use extra cash to pay down student loans, take out a full mortgage. Use extra cash to make a big down payment on the next house, keep paying down student loans at normal rate. In both scenarios the student loan rate will  stay the same. However in the second scenario you may get a lower interest rate from making a larger down payment. So then calculate the total interest resulting from each scenario: student loan rateXremaining student loan balance=student loan interest  new mortgage rateXnew mortgage balance=mortgage interest scenario 1 interest = student loan interest+mortgage interest student loan rateXstudent loan balance = student loan interest  new mortgage rate with large down paymentXnew mortgage balance after large down payment = mortgage interest scenario 2 interest = student loan interest+mortgage interest Whichever scenario's interest is lower will save money. Line one shows your 1M, a return with a given rate, and year end withdrawal starting at 25,000.  So Line 2 starts with that balance, applies the rate again, and shows the higher withdrawal, by 3%/yr.  In Column one, I show the cumulative effect of the 3% inflation, and the last number in this column is the final balance (903K) but divided by the cumulative inflation.  To summarize - if you simply get the return of inflation, and start by spending just that amount, you'll find that after 20 years, you have half your real value.  The 1.029 is a trial and error method, as I don't know how a finance calculator would handle such a payment flow. I can load the sheet somewhere if you'd like.  Note: This is not exactly what the OP was looking for. If the concept is useful, I'll let it stand. If not, downvotes are welcome and I'll delete. nowhere near enough information to really help you.  Price it to an IRR of about 25% in 4 years as your business has little to no history.  For small business in most sectors you can use a rule of thumb, 2x net + FFE.  For me personally, I wouldn't touch a business only 6 months old. "The bank ""credit's"" your account for money coming into it. In double entry accounting, you always have a debit and a credit to balance the accounts. As an Example: for $500 that the bank credited to your checking account, you would post a debit to Cash and a Credit to Income Earned. The accounting equation is: Assets = Liabilities + Owner's Equity                             $500   =                    $500 Cash is the ""Asset"" side of the equation, Income is part of Owner's Equity, and so is the Credit side... to make the equation balanced." Thanks for this, great in depth answer. I had previously calculated a WACC and have used it for my discount rate.   As part of your last point on revenue vs. cash, I've set a accounts receivable period of 30 days, and then applied a factor of 30/365 * revenue to understand what portion of my revenue is not cash in hand. Does that make sense? "A lot of financial software will calculate the value of operating leasess for you (bullet 2). E.g. Capital IQ, BB.   What a lot of professionals do is ""reverse"" out EBITDA/EBIT etc. for:  - non-recurring expenses (think big accounting changes, some impairments) - change operating expenses into capital leases to adjust the capital structure - occasionally change some operating expenses (e.g. options) because you are under the assumption if you take a company private that those expenses will not be relevant  The whole point is simply to see the operating revenues/expenses of the firm"