If you received the check in December of 2017, but you didn't deposit the check until January 2018, It would have been taxable to you in 2017 because as a cash basis taxpayer income is constructively received when it is made available to you without restriction. You can't hold a check until the next year to deposit (well, you can, but it still counts as income in 2017). Likewise, whatever the client paid you in 2017 should be on the 2017 1099-MISC, and not on your 2018 1099-MISC from that same client.
Don't you show in QuickBooks where your income came from? Usually, when you receive a payment it's linked to a customer. You should be able to review your income from both years to figure out if the 1099's from your client are correct. You should report the correct income no matter what the 1099's say because your records should show the correct amount. If 2017's income was reported incorrectly, you'll need to amend your return.
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