Interstate Common Line Support (ICLS) is available only to rate-of-return incumbent carriers (mostly rural and some non-rural carriers) and competitive carriers providing service in the areas of these companies, which must be designated as eligible telecommunications carriers (ETCs) by their state commissions or the Federal Communications Commission (FCC).
ICLS helps to offset interstate access charges and is designed to permit each rate-of-return carrier to recover its common line revenue requirement, while ensuring that its subscriber line charges (SLCs) remain affordable to its customers.
ICLS is based on annual projected data submitted by incumbent carriers each March 31 and is subject to an annual true-up process based on actual data submitted by incumbent carriers each December 31 for the previous calendar year. Because competitive carriers receive ICLS based on the incumbent carriers' data filings, which are used to calculate per-line rates, competitive carriers do not need to file projected or true-up data for ICLS.
The ICLS Annual Common Line Actual Cost Data Collection Form, FCC Form 509, is due annually on December 31. The ICLS Projected Annual Common Line Requirement Form, FCC Form 508, is due annually on March 31. Revisions to FCC Form 508 are due on June 30 for the current or previous Program Year.
ICLS is covered in Subpart K of Part 54 of the FCC's rules (47 CFR Section 54.901 et seq.)