Colorado taxpayers are being told to pay up, except for one minor problem.

The Colorado Department of Revenue sent out 9,000 bills this past week without the payment coupon detailing how much is owed.

The bills are called "Notice of Deficiency or Rejection of Refund Claim." Essentially, they are tax bills.

"I kept looking through the envelope to see if I had missed some little slip of paper," said Denver resident Anne, who tipped us off to the mistakes.

"When we went to send out these notices, it printed out the first page, but not the second page that was supposed to be attached to that first page," said Department of Revenue spokeswoman Lynn Granger.

The second page was supposed to include an "attached payment coupon" indicating how much that taxpayer owes. It was missing on the first batch of 100,000 mailings.

"It was roughly 9,000," said Granger. "Those customers that are affected should be seeing that second page come in a second mailing in the next two to three business days."

Next wanted to know how much it costs to send 9,000 additional letters.

"It'll be roughly $4,500 to send out that additional mailing," said Granger. "Is it OK? No, we always aim to provide the best possible customer service. We're not perfect. We do have errors sometimes, unfortunately, and we apologize for any inconvenience that this causes customers."

Anne's inconvenience was more than 20 minutes on hold and another 10 minutes figuring out the dollar amount.

"The person who helped me was very nice and was able to look up what the amount was," said Anne. "I owed $57."

She reached out because she wanted the Department of Revenue to put a banner on its website or a new recording on hold indicating the problem and letting taxpayers know they would be getting the payment coupon in the mail shortly.

"If we all spent at least 20 minutes on hold, that's over 3,000 hours' worth of time that citizens would have wasted," said Anne. "Not to mention the people who are working there having to waste time telling each person over and over that it was their mistake."

Granger said the Department of Revenue was working on those suggestions to help taxpayers know the rest of the mail is coming.