I have been paying into a tax free index tracking account for a number of years, the amounts were only occasionally regular and varying in size. I haven't withdrawn anything.

I have exported data from the provider's website, so I know how much I have paid in over the years, and the date of each transaction.

The current value is a healthy amount higher than my contributions so I know it has grown, but is there any way to get an average interest rate or something, so I can compare my current price and transaction log with hypothetical performance if I had paid the same amounts on the same dates into fixed rate account?

There are countless calculators online that take a lump sum value and/or a monthly amount and an interest rate and spit out an answer, but I can't find anything capable of proving whether I would have been better or worse off with a safer account that won't fall with the markets.

  • 1
    What index is it tracking? Are you saying that the current balance is the same at the total of all of your contributions? To answer the question, Excel's XIRR function can calculate the rate of return with varying cash flow amounts and dates. – D Stanley Jul 3 '18 at 13:36
  • I don't have a real answer for you, but if the amounts and dates you put into it are essentially random (i.e. tied to your personal finances and not speculation on the market) then the law of large numbers says your return will be approximately the same as the funds average X year return. Some of them probably got lucky by buying before the index rose, and some probably unlucky by buying before the index fell, and probably with the same consistency. – corsiKa Jul 3 '18 at 14:48
  • I have edited my question to hopefully make it clearer. The current value is higher than my contributions, I just wanted to quantify the growth. @corsiKa I can compare to fund managers report of the rate, but I could do that for any fund without investing, I would like some concrete figures based from my personal experience. I was suggesting this system to someone and want to put my money where my mouth is! Comparing with the official results gets trickier because the money is split across different funds in the same isa wrapper – CodeMonkey Jul 3 '18 at 19:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.