Processing the check is IRS's responsibility. If they accepted your check, but do not process it, it is their fault. Once they accept your check, your end of the deal has ended. A while back, I got a notice that I did not pay my state tax.
1 The xiphoid process (Latin: processes xiphoideus) is a small triangular cartilaginous extension of the breastbone.
Xiphoid Process and CPR. Care should be taken not to put any pressure on the Xiphoid Process during cardiopulmonary resuscitation (CPR). It is an unsupported structure and can break off under pressure. A broken Xiphoid can damage various internal organs and cause serious pain and inflammation in the chest. There are many CPR hand positions that are unsafe for women as the hand extends past the sternum base in these positions. These hand positions increase the risk of breaking the Xiphoid Process.