Is it true paying a lump sum into an investment ISA risks low profit, but regular small payments spreads risk?

I’ve been told by an advisor at the Hallifax that the reason my investment ISA went down in value is because I paid my full allocation in one lump sum. By paying the same amount in regular small amounts, I could have spread the stockmarket-related risk to the point of virtually guaranteeing 10-20% profit. This is assuming I understood the nice lady correctly! Does that sound right? If so, What’s the optimum amount to pay in? Would paying in weekly be more profitable than monthly?

if the market goes down, then yes your risk is reduce because you are averaging in, that is being able to buy more share with the same amount of allotted money.

however if the market keeps going up you’re buying less but still making money on the way up.

this type of investing is usually on a 3 to 5 year time-horizon and you should not invest money you need right now to live off and pay bills etc

there is no optimum, the market are always changing, they are the sum of everyone fear and greed…so the market is irrational and cannot be approached in a rational manner even thought many people think they know what they are doing.

i would suggest you put in a equal amount every month…most institution track the market on a weekly and/or month timeframe