I need to find missing invoice numbers from an unorganized list with non-unique entries.

Dear Excel Forum

I have searched for this and found many threads, but do not know how to apply the answers.

I have a list of invoices that I have entered into an excel document, they are in fields A2:A303, but the list will get longer as I add more invoices.

My invoices are not in numerical order, and there are non-unique entries of the invoice number.

Sometimes, since some invoices are paid earlier than others, I can have an invoice number that is 10-15 numbers ahead of the rest. For example

3001
3002
3016
3004

I'm afraid I may have accidentally forgotten to enter certain invoices, so I need to somehow create a list of invoices that I have missed out in a new column. Admittedly, the list may show numbers 3005-3016, even though I may have not received payments for them yet.

Please advise and I will be forever greatful.

Thank You