The U.S. Postal Service may delay postmarking for tax returns mailed near the April 15 deadline due to operational changes at the service. The IRS considers any tax return postmarked on or before that date as being filed on time, even if it's not received by the agency days later. This is due to ongoing operational changes within the Postal Service, which have resulted in an increase in delays due to reduced pickups at many postal locations and increased travel times for mail to reach regional processing centers where postmarks are applied. The Postal Service has added language to its Domestic Mail Manual to clarify this issue. For individual tax returns, the penalty for filing a late return is 5% of the tax due for each month or partial month, capped at 25%. Interest is also charged on unpaid balances. However, if you have filed and paid taxes owed on time over the previous three years, you can request that the penalties be waived.