I heard on the radio recently that if one applies for an automobile loan or a home mortgage, multiple loan applications show up as one hard pull on your credit report. Is there a time period where all the hard pulls are merged together? The radio said a short period of time, but that is vague. Does anyone know the specifics?
This phenomenon is called rate shopping. It is very hard to tell the specifics as each model will have its own thresholds.
For example, for FICO models, they have a 30 days window period for mortgage, auto, and student loans. But in some circumstances they may consider any similar inquiries outside this window as well.
In addition, the score looks on your credit report for mortgage, auto, and student loan inquiries older than 30 days. If it finds some, it counts those inquiries that fall in a typical shopping period as just one inquiry when determining your score.
Too many inquiries may have a negative impact on your credit score. However, most recently developed credit scores recognize when a consumer is shopping for the best rates and either ignore multiple inquiries or count them as only one inquiry if they occur within a specific period of time. In such cases, shopping around will have little or no impact on a credit score.
So as you can see, every model has a different approach and it is hard to make a concrete rule out of this. But as a thumb rule, try to keep it within a month and you should be okay. Also mind that this luxury is not available for credit card inquiries but only for loan inquiries.