Generally when tasks such as running reports and saving invoices starts to slow to a crawl, it means your Quickbook’s company file is starting to get too big; that it has too many entries over many years. Upon discovering this, our first instinct is to Google ways to shrink our company file. We then find that the only way to really do this is by creating a new company file and performing a lot of manual re-entry or paying a company to do this for us. However, asking how to shrink this file is actually the wrong question. What should be done is to archive the file. Archiving does not significantly shrink the size of the file, but it does significantly speed things up. Several things should be done when it is just too painful to maintain the books:
1) Verify the integrity of the company file
2) Rebuild the company file using Quickbooks built-in function (backup the file when prompted)
3) Verify the integrity of the company file to make sure the repair function fixed all the issues
4) Re-run the rebuild tool if it did not (Create a separate backup each time)
5) Repeat the verification and repair processes up to three times. If the company file is still damaged make a support call to Intuit to get the file repaired. Even if you do not have a support contract with them, you can pay for support on an as needed basis.
6) Archive the company file 1 year at a time until 2 years remain (previous and current).
Read the below article before performing these tasks:
http://support.quickbooks.intuit.com/support/pages/knowledgebasearticles/1002282