Can it keep the next check number in sequence?

Yes, QuickBooks will automatically sequence the check numbers for easy tracking, C.

In QuickBooks Online (QBO), you can reset the check number sequence according to your preference. But before doing so, there were steps you needed to enable in the settings.

Here's how:

1. Go to the Gear icon settings and select Account and Settings.
2. Select the Sales tab, click the pencil icon, then choose Sales form content.
3. Turn on the Custom transaction numbers, and click Save.
4. Once done, go to the Advanced tab from the same page.
5. Click the Other preferences section.
6. Toggle the Warn if duplicate check number is used option.
7. Click Save and then Done.

Once done, you can create a new check after adjusting your settings.

If you want to figure out which check numbers have been used in QuickBooks so far, check out the guide here on creating a check number report to help you sort them.  

Please don't hesitate to notify me if you have any additional questions about check sequence or concerns in QuickBooks. I'll be around to help you anytime.