2 questions on number sequence and dates

Newbie to Excel and have created a simple check register. My first question is how to write a formula that will increase the check number by 1 when "entering the check# cell" column. sometimes I may make several entries without using a check # before I need to enter the next check. I was using quickbooks and it would automatically update the next check number when I entered the check number cell.

Second question is how can I format a date in a cell that allows me to enter a number that will default to the date format when leaving the date cell. Example: I type in 11082021 and when I tab from the cell it automatically formats to 11/08/2021.

Thanks for any help.
Mike

Thank you for your response, I understand about the date issue. Let me be more clear on my sequence question. "Column A" is "Date", "Column B" is "chk number". As I make entries into my register in the "rows"
I enter the date in column A and then if I have a check to enter I would like the next check number to automatically appear in Column B based on a prior check that was entered. My issue is I don't always need
to enter a check number for every transaction. I use my debit card quite a bit so I don't need to enter a check number for that transaction. Consequently, my last check entered might be "Column B row 15" but
the next check might be "Column B row 20". How would I write a formula that would look at Column B row 15 and enter the next check number in Column B row 20?

I'm sure I've got you totally confused by now and I do appreciate any help you can provide.
Mike

There are instructions at the top of the page on how to post a sample sheet.Thanks

In B2 you can enter this formula and copy down:

=IF(A2="","",MAX(B$1:B1)+1)

If you don't want the check number for that date entry, delete it and the next row then will get the next one.

Thank you for your reply. It worked perfectly. Issue is solved.