Physical therapy billing uses time-based units, where each unit typically represents 15 minutes of direct patient care. Tracking these units accurately is essential for proper reimbursement and compliance with payer rules.

Medicare and most insurance companies follow the 8-minute rule for timed CPT codes. If a therapist provides between 8 and 22 minutes of a timed service, that counts as one unit. From 23 to 37 minutes is two units. The pattern continues in 15-minute increments. Anything under 8 minutes for a single timed service cannot be billed as a unit on its own.

The calculation gets more complex when multiple timed services are provided in the same session. The total treatment time across all timed codes determines the total units allowed. A therapist who provides 20 minutes of therapeutic exercise and 15 minutes of manual therapy has 35 total minutes of timed services. Using standard unit calculation tables, that translates to a specific number of billable units split between the two codes based on time spent on each.

Therapists track time by documenting start and stop times for each service within a session. Some practices use their EMR system to log this automatically as therapists move through treatment. Others rely on therapists to record times manually in their notes. Either way, the documentation needs to support the units billed. If an audit occurs, payers will compare the time recorded in clinical notes to the units submitted on claims.

Untimed codes work differently. Services like evaluations, re-evaluations, and group therapy are billed as one unit regardless of time spent. These don’t follow the 8-minute rule. Knowing which codes are timed and which are untimed prevents common billing errors.

The financial impact of inaccurate unit tracking adds up quickly. Underbilling by even one unit per patient across a busy practice means significant lost revenue over a month. Overbilling creates compliance risk and potential payback demands from insurance companies. Practices that handle their own medical billing need someone reviewing documentation and calculating units before claims go out.

The connection to bookkeeping matters because revenue depends on getting this right. If claims are underbilled or denied due to documentation gaps, the revenue you expect doesn’t match what actually comes in. Working with Macomb, MI bookkeepers who understand healthcare billing helps catch discrepancies between billed services and posted payments before small problems become big ones.

Most practices build unit tracking into their daily workflow. The therapist documents treatment time during or immediately after each session. Someone reviews the documentation for completeness before billing. Regular reconciliation between billed units, paid claims, and posted payments identifies patterns that need attention.