What do you think about Accurate Sales Forecast? Is it something we can rely on for business plan ?

Accurate Sales Forecasts can be relied on to an extent based on some crucial key factors. 

A/ Is the Sales Forecast being presented from this person/group reliable and credible?

B/ Is the person presenting the Sales Forecast normally accurate?

C/ How recent are the numbers provided in the Sales Forecast? Are they from last month or last night?

By getting to know the persons presenting the forecasts and aligning this with your own market research, facts and figures, should stare you in the right direction.

As a safe guard it is never best to "count" on an accurate Sales Forecasts as there are so many variables which can contribute to the numbers in either direction.   

its very important that this sales forecasting especially in many companies, so they can predict or prevent in the future of their sales in different account in the company, they can make cash flow effectively they can see what is wrong and what is right, they can know or plan whats next or what it will be.