I would like to know the expiration date (within 6 months) of several older patents which expired because the fees stopped being paid. I am missing an input to figuring out the expiration date, namely the date the assignee stopped paying fees, so here is the information I have to work with,
- The USPTO patent term calculator, a spreadsheet which calculates the expiration date from user-entered data. It lists the dates of several sets of maintenance fees due 4, 8 and 12 years after issue. I am supposed to enter which of these fees were skipped (don't know) in order for it to predict the expiration date.
- The Public Patent Application Information Retrieval (PAIRS) "Application Data" tab retrieved in a search for the patent by number. PAIRS lists the status as "Patent Expired Due to NonPayment of Maintenance Fees". It gives a "status date" which seems to be when the status was checked, but not when the patent actually expired,
- The PAIRS "Transaction history" tab in the search results, which includes "Issue Fee Payment Verified" transactions, but does not seem to include the maintenance fee transaction dates which I need for the patent term calculator,
- The PAIRS "Transaction history" tab also lists a date for an "Expire Patent" transaction. Is this the actual expiration date? I can't find a definition on the PAIRS website, and it differs from the spreadsheet output by a bit (a month or so).
- The Google Patent entry for the patent, which lists the "Anticipated expiration" date.
Here is how I am proceeding. Please let me know if it's wrong.
- Get the maintenance fee dates from the patent term calculator.
- Get the status date from PAIRS. Since the status is expired, assume the fees stopped being paid at the last due before the status date. For example, if fees were due 2000, 2008, and 2012, and the status date was 2009, assume the dues were paid in 2000 but not in 2008 or 2012.
- Plug the unpaid fees date from #2 into #1, and get the expiration date. This can differ from Google's "anticipated expiration" date by many years!
Is this enough to get me within 6 months of the actual expiration date? Can I just use the "Expire Patent" date from PAIRS and skip the calculation?