NARA - Compiled Military Service Records War of 1812.

The great majority of soldiers who served during the War of 1812 were volunteers, or members of state militia who were federalized for portions of the war period. There were also volunteer units directly raised by the federal government. The service records of these soldiers consist of compiled military service records or those records of service that were compiled from the original muster and pay rolls by the clerks in the Adjutant General's Office after the war (Records of the Adjutant General's Office, Record Group 94). State or federal volunteer unit arranges the records and they’re under alphabetically by name of soldier. A microfilmed index to these records is available on Index to Compiled Service Records of Volunteer Soldiers who served during the War of 1812 (M602, 234 rolls). The actual service records have not been filmed. The service records show the soldier's name, rank, regimental unit (usually showing the last name of the regimental commander), the company commander's name, dates of service and pay, whether the soldier was a substitute, date of discharge, and sometimes, distance to the soldier's home from place of discharge. 

Other information such as date of death, if applicable, and periods of sickness, if recorded on the muster rolls, is noted. The service record reflects the information found on the original muster and payrolls; all information from these original rolls has been transferred to the compiled service record, so there is no need to examine the original rolls to obtain additional information. Because so many volunteers served only a few days or weeks, the information available is frequently meager. These records will not ordinarily show place of birth, age, or parents' names. They may show, however, disciplinary action resulting in dismissal or court-martial, if such information was noted on the muster roll. Compiled service records for officers show much the same information but usually include original vouchers and receipts for supply, pay, and transportation. Some of these papers may enable a researcher to determine where a unit served during the war.