Copying information from one cell in one to another worksheet.

Yes. If you have each transaction as a row eg:
Date|Customer name|Invoice Amount|
And your costs sheet might look like:
|Date|Customer Info|My Cost|Supplier|Tax|
In the costs sheet, click the first empty cell below the Customer Info heading and press the = key, switch back to the Invoices tab and click the cell you want to get the customer information from. Press enter. You have just linked a cell in your costs tab to the cell in the invoices tab.
Click the same cell in the My Costs tab again- there will be a little square in the bottom right corner. Drag that square down the column to the size you desire for the number of transactions- this will link the same cells on the Invoices tab so that when you enter information into them, the same info will appear in the My Costs tab. There are a number of ways to achieve the same thing- have a google for "fill down" (CTRL-D) and cell references.

This might also be handy:
https://support.office.com/en-us/article/create-or-change-a-cell-reference-c7b8b95d-c594-4488-947e-c835903cebaa#bmcreate_a_cell_reference_to_another_wo