My customer initiated a payment / deposit 3 days ago and I don't see it as of this morning. How long should my for deposit to show up?

It's great that you're utilizing the online payments function through QuickBooks Payments, Mike. The first time you receive the online payment usually takes 5-7 business days. 

It is longer the first time because the system is still setting up your account. Also, the system is reviewing the processed payment to prevent any fraudulent activities. Rest assured, the next time you receive payments from your customers will be processed faster. You can use this link for reference: Find out when QuickBooks Payments deposits customer payments.

With the article above, it is also mentioned how you can check the deposit speed, schedules, and statuses. You can also go to your Merchant Services Center to review the status of the deposits.

If you want way faster than the regular deposit process, you can for an instant deposit by following the steps in this article: Get instant deposits in QuickBooks Online.

Let us know if you need additional assistance in tracing your deposits so we can get you around it. Have a great day!