Track membership fee belated
You can make use of the "Date Renewal Entered" field for this purpose - e.g. if you enter a date of July 1, 2018, then a 6 month membership will be extended through December 31, 2018 - the date the payment was recorded can be left as the current date - when you click to view the membership, it will appear as displayed in the screenshot below:



Hope this helps!