Hi telamamare,
I'm happy you're here. I'd love to share some information about changing the payment date of your customer checks.
Yes, you can change the date of these transactions to match the actual date you received the payments. It won't impact or cause any errors on your books after you correct the dates as long as it coincides within your reconciliation period.
If it doesn't, undo
the reconciliation where this transaction is involved and re-reconcile them again. This is to ensure that your books are accurate and there won't be any discrepancies later on.
I'd also recommend you reach out to your accountant. Your accountant should be able to provide you more expert advice on how to handle these transactions.
Feel free to keep in touch if there's anything else I can do for you. I'm here anytime you need help with QBO.