"Agency" on a debt transaction is not one job but several, each handling a distinct part of keeping the deal running. On any given facility you may see a facility agent, a security agent or trustee, a paying agent, a calculation agent and a registrar — sometimes all held by the same provider, sometimes split between several.
The core roles
The paying agent receives funds from the issuer and distributes them to investors — coupons, interest and redemptions — on the dates the documents require. The calculation agent works out the amounts: interest accruals, rate resets and any formula-driven payments, so the paying agent has the correct figures to settle. The registrar maintains the register of holders, recording who owns the securities and updating it as positions transfer.
The registrar knows who is owed; the calculation agent knows how much; the paying agent moves the money.
Why it helps to consolidate
These roles interlock. The registrar knows who is owed; the calculation agent knows how much; the paying agent moves the money. Holding them with a single independent provider reduces the points of friction and the risk of information falling between parties — one team with a complete view of the deal rather than several with partial ones. As with facility agency, an independent provider avoids the conflicts that arise when a lender or arranger also performs these functions.