The system currently has a limit of submitting 35 receipts within a 7-day period.
This 35 receipt limit is based on the date you snap the receipt, not the checkout date. This simply means that over a rolling 7-day period, you can snap up to 35 receipts. If you hit that limit, you can snap more of your receipts as the oldest of your receipts fall outside of that 7-day window.
If you are waiting to upload a receipt with a special offer, it will still be awarded points as long as the checkout date is within the offer timeline. eReceipts that are processed on your account will not count towards this 35 receipt limit.