Thanks on advance for your response. First off, a little backstory. For a very short time I was a real estate agent locally. My local office charged monthly fees and when I went inactive they continued to bill me. After that contacted me months later about the balance I contacted their accounting and explained the situation and told it would be taken care of. More than a year later I was contacted by the person in charge of the office by email. I explained this should have been taken care of. He emailed accounting and after I heard nothing back I emailed him for an update. I never got one and haven't heard from him in 9 months, so I assumed it had been taken care of. Today I received a letter from a debt collector. I want to fight this but I'm worried it will hit my credit while I'm fighting it and I've worked too hard to have this screw me up. This letter says I have 30 days to dispute the validity of this debt, so does that mean they aren't going to report to the credit bureaus until after that 30 days or is it likely they already have?
A debt collector can report their collection to the CRA at any time after they obtain collection authority, including prior to sending any notice to the consumer, unless they are under a cease collection bar.
They could have reported prior to sending you the initial collection ("dunning") notice, so no, they are not barred from reporting their collection.
The statement that you have 30-days to dispute the validity of the debt is a standard requirement in any dunning notice (see FDCPA 809(a)), and does not preclude reporting during that period. Many debt collectors will not report until after the period for requesting debt validation has expired, but they are not legally precluded from doing so.
If you do send a DV request within that 30-day period, it then imposes an automatic cease collection bar on the debt collector, which remains in effect until they first send the requested debt validation. See FDCPA 809(b).
If you send a timely DV, case law interpretation in most states has held that reporting to a CRA then becomes a violation of the cease collection bar, so if they have not yet reported and you send a timely DV, you will likely bar reporting until they have first sent validation.
Howver, they can send validation immediately upon receipt of your DV request, and then report the same day, so any bar in reporting is only temporary, and beyond your control.