Is it permissible to estimate the amount of Zakat due for the the past three years in the event that a complete archive is not available to calculate it precisely?

You must strive and investigate to the best of your ability to ascertain what is due from you in Zakat, so that you may clear your conscience before Allah and distribute it to those who are deserving; for Allah the Almighty said: ﴿Allah does not charge a soul except [with that within] its capacity.﴾