Student receivables represent funds owed to us in exchange for the educational services provided to a student. Student receivables are reflected net of an allowance for doubtful accounts at the end of the reporting period. Student receivables, net, are reflected on our consolidated balance sheets as components of both current and non-current assets. We do not charge interest or fees on any of our payment plans.

Generally, a student receivable balance is written off once a student is out of school and it reaches greater than 90 days past due. Although we analyze past due receivables, it is not practical to provide an aging of our non-current student receivable balances as a result of the methodology used in determining our earned student receivable balances. Student receivables are recognized on our consolidated balance sheets as they are deemed earned over the course of a student’s program and/or term, and therefore cash collections are not applied against specifically dated transactions.

Our standard student receivable allowance estimation methodology considers a number of factors that, based on our collection experience, we believe have an impact on our repayment risk and ability to collect student receivables. Changes in the trends in any of these factors may impact our estimate of the allowance for doubtful accounts. These factors include, but are not limited to: internal repayment history, changes in the current economic, legislative or regulatory environments and the ability to complete the federal financial aid process with the student. These factors are monitored and assessed on a regular basis. Overall, our allowance estimation process for student receivables is validated by trending analysis and comparing estimated and actual performance over a 12 month and 24 month period.

As of December 31, 2019 and 2018, the amount of non-current student receivables under payment plans that are longer than 12 months in duration, net of allowance for doubtful accounts, was $1.2 million and $0.9 million, respectively.

Changes in our current and non-current receivables allowance for the years ended December 31, 2019, 2018 and 2017 were as follows (dollars in thousands):

	Balance, Beginning of Period		Charges to Expense ⁽¹⁾		Amounts Written-off			Balance, End of Period
For the year ended December 31, 2019	$	24,836	$	43,470	$	(36,342	)	$	31,964
For the year ended December 31, 2018	$	22,534	$	32,042	$	(29,740	)	$	24,836
For the year ended December 31, 2017	$	23,142	$	27,571	$	(28,179	)	$	22,534

The carrying amount reported in our consolidated balance sheets for the current portion of student receivables approximates fair value because of the nature of these financial instruments as they generally have short maturity periods. It is not practicable to estimate the fair value of the non-current portion of student receivables, since observable market data is not readily available, and no reasonable estimation methodology exists.