How do you calculate the portion of telephone expense if I work from home?

[bmowery2015]

Last year I claimed my whole phone bill. Has this changed?

[Opus 17]

You can't do that (and shouldn't have done that) unless you have a separate work-only phone line.

For a household phone (land line) that is used for business and personal use, you can only deduct the amount of costs that are caused by the business that are more than your personal use.  So if you pay a flat rate that includes long distance, and would pay the same even if you had no business use, then you can't deduct your business use.  You can claim your business calls as work expenses if they are billed separately and increase your cost (bill by call, or bill by the minute, or extra long distance calls) if you have records to prove your costs.