Ok let me explain.

For e.g. user A has updated rows 2 to 20 on his file in week 1 and this has been added to the master file. Now, in week 2, he realises that he made a mistake so corrects week 1 data. In this case, if the macro is setup to only copy new rows that get entered, the error will not be corrected in the data.

However, if we copy the data from row 2 onwards directly into the master file, it will create duplicate records since there was already data for wk 1 there. So if we clear the data and then update, no duplicates will occur and also the errors will be corrected.