For Medicare B patients, and this goes to coinsurance and deductible amounts, Medicare REQUIRES a "reasonable collection effort" which is industry-defined as 3 billing cycles. Anti-kickback statutes and even the False Claims Act can be invoked to prosecute physicians that routinely do not make this effort. The mindset being that the claim is for an inflated amount if the provider does not collect coinsurance amounts hence, the bill should have been sent to Medicare for the "reduced rate".
For other payers, in our area the prevalent two being MVP and CDPHP, the specific language regarding collection of copays and/or deductibles is in the fine print of the provider enrollment contract. Again, you MUST collect the copays! Failure to do so can result in the loss of your payer contracts.
The ONLY times is it acceptable to "waive" copayment or deductible amounts are after reasonable collection efforts fail or in the case of DOCUMENTED indigence of the patient. Practices will often have an indigence waiver for this purpose.
Hope this helps.