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.

  1. Get the maintenance fee dates from the patent term calculator.
  2. 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.
  3. 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?

  • You might want to look at the actual law. I'm no US patent attorney so I'd have to look it up too. But law is a very formal thing. This gives you the payable maintenance fees. Then you need to find the information about actually paid maintenance fees. Those are surely accessible somewhere official. This gives you the actual expiration date. From there, try working backwards to figure out if the same information is derivable from the information you have available.
    – user18033
    May 3, 2021 at 18:55
  • I haven't been able to find a public website (PAIRS or elsewhere) that lists when the maintenance fees were paid. If anyone comes across this, please let me know.
    – KAE
    May 3, 2021 at 19:16
  • 1
    You can look up the maintenance payment history here fees.uspto.gov/MaintenanceFees
    – George White
    May 3, 2021 at 23:46
  • If you are trying to find expiration dates of patents, please see my comment in the accepted answer below for a much easier method than what I describe in the question.
    – KAE
    May 4, 2021 at 12:57

1 Answer 1


You can look up the maintenance payment history here

And - From the MPEP

Therefore, if the maintenance fee and any applicable surcharge are not paid, the patent will expire as of the end of the grace period as listed above. A patent that expires for failure of payment will expire on the day following the anniversary date the patent was granted in the 4th, 8th, or 12th year after the grant.

  • Many thanks. For others: you will need both the patent number, and the patent application number, to look up the payment history. If you only have the patent number, enter it in PAIRS, and the application number will be listed in the upper left. Note the payment history here only seems to list the maintenance fee payment dates if the assignee stopped paying them. A paid-up patent that expired at the end of its lifetime will just say that no maintenance fees are due.
    – KAE
    May 4, 2021 at 12:39
  • The payment history here actually lists the expiration date of an expired patent!! For example, "Patent expired on 04/25/2007 due to non-payment of maintenance fee." No patent term calculator needed!
    – KAE
    May 4, 2021 at 12:54

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