Mercury vs Relay: Banking for a PR and Communications Agency
Most PR and communications agencies run on retainer revenue, which makes month-to-month cash fairly predictable compared with a project-only business. What's less predictable is the irregular cost that shows up around a launch event, a press trip, or a client crisis that suddenly needs a team working overtime and vendors paid fast.
That mix, a stable base plus occasional cost spikes tied to specific moments, is what this comparison is built around.
Vendors Covered in this Article
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Keep Retainer Revenue Separate From Event Pass-Through Costs
Agencies that run client events, a product launch, a press trip, a media dinner, often front venue deposits, travel and vendor costs that get billed back to the client as part of the engagement. Mixing that pass-through cost into general retainer revenue makes it hard to see the agency's actual earned margin once event season gets busy. Relay's free sub-accounts make separating the two straightforward: retainer fees land in an operating account, event pass-through costs route through a dedicated account funded by the client's event budget specifically, and the agency's true margin stays visible even during a heavy event quarter.
Build a Standing Crisis Response Reserve
A client crisis, a product recall, an executive departure, a data breach, can require an agency to staff up fast, sometimes bringing in freelance support or working weekends, before that additional cost is billed and collected. A dedicated crisis response reserve, funded from a slice of retainer revenue and kept separate from day-to-day operating cash, means the agency can respond immediately without waiting on a change order to clear first. Mercury supports the same structure through its own multiple accounts, with the added benefit of an API for an agency running a client services platform that tracks retainer scope and overage together.
What Idle Reserve Cash Should Be Earning
A well-funded crisis reserve sits unused for long stretches between actual crises, and that idle cash is worth earning something on. The effective federal funds rate is at 3.63%1 today, and Mercury's automated Treasury sweep captures yield near that level on cash above your working buffer, a reasonable fit for a reserve that needs to stay liquid but isn't touched for months at a time. Relay's savings sub-accounts pay a published rate too, without the same automated sweep into short duration Treasury instruments specifically.
Financing an Event Season Without Overpaying
An agency bridging a heavy event season, several client launches clustered in the same quarter, with a short-term credit line is borrowing at a cost tied to the bank prime rate, currently 6.75%2. Before drawing on a line every event season, check whether event pass-through billing is actually collecting fast enough from clients; a chronic gap between fronting event costs and collecting reimbursement is often a contract terms problem, a deposit required up front rather than billed after the fact, that's cheaper to fix than to finance around indefinitely.
Choosing Based on Team Structure
An agency with an ops or client services platform already tracking retainer scope, overage and event budgets gets real value from Mercury's API, connecting banking data directly to that system. A smaller agency running client budgets out of a spreadsheet alongside QuickBooks or Xero can often start with Relay, whose accounting integrations and extra checking accounts on the free plan (up to 20 per business per its pricing page) may cover the need without custom integration work.
A Quarterly Check Worth Keeping on the Calendar
Review the crisis reserve and event pass-through structure every quarter, not just when a crisis or event forces the question. Confirm the crisis reserve is still sized against current retainer volume and team size, since an agency that's grown its client roster without growing the reserve is carrying more risk than it realizes. Confirm event pass-through accounts are actually being reconciled against client billing regularly rather than left to accumulate until a launch is over and everyone's too busy with the next one to look back.
At each quarterly review, confirm the following:
- The crisis reserve is still sized against current retainer volume and team size, especially if the client roster has grown faster than headcount.
- Event pass-through costs are still tracked apart from retainer revenue, so front-loaded venue and travel spending never looks like operating income.
- Any credit line drawn for a heavy event season is still needed and is priced against the current prime rate, not used out of habit.
- Each account has a named owner who understands how funding and reconciliation work, so a new hire can follow the process.
What a New Business Win Should Trigger
Landing a new retainer client, especially one in a higher-risk category, consumer products with recall exposure, a public company with disclosure sensitivity, is worth treating as a trigger to revisit the crisis reserve sizing immediately rather than waiting for the next scheduled quarterly review. An agency that adds a meaningfully riskier client to its roster without adjusting its reserve is carrying exposure nobody has actually sized for that specific relationship, and that's exactly the kind of gap that only becomes visible once a real crisis is already underway.
Documenting the Setup for a Growing Team
As an agency adds account managers and client leads, write down how event pass-through and crisis reserve accounts actually work, which account funds what, how reconciliation happens, and who owns it, so a new hire can follow the process without reconstructing it from institutional memory. Agencies that keep this knowledge in one senior person's head are the ones most exposed when that person is unavailable exactly when a crisis reserve needs to be tapped quickly.
What Good Looks Like
A well-run agency can show, for any client, retainer revenue separate from event pass-through costs, and can state its current crisis response reserve balance against its client roster's risk profile at any time.
Building The Capability (5-Stage Skill Ladder)
How to Get Started
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Mercury fits an agency running a client services platform worth connecting through an API, or one with a crisis reserve worth sweeping into yield.
Relay fits most agencies first: free dedicated sub-accounts per client keep event pass-through and retainer revenue cleanly separated.
Brex fits for smaller ad hoc purchases and staff expenses during an event that don't run through a formal vendor account.
Frequently Asked Questions
Should crisis response work be billed differently than routine retainer work?
Most agencies bill crisis response as an overage above the standard retainer scope, sometimes at a premium rate reflecting the urgency and after-hours nature of the work. Whatever the policy, write it into client contracts up front so it's not being negotiated for the first time in the middle of an actual crisis.
How large should a crisis response reserve be?
Size it against roughly what it would cost to staff up for your most demanding realistic client crisis for a week or two, not an average month, since the risk you're covering is one intense situation, not steady state operations. Revisit the number as your client roster and its risk profile change.
Is Brex useful for an agency that already has vendor accounts for event venues and travel?
It helps for smaller ad hoc purchases and staff expenses during an event that don't run through a formal vendor account. It doesn't replace negotiated terms you already have with major venues or travel vendors for recurring event work.
Sources
Where we quote a benchmark, we show its source. Other figures in this guide are estimates or general guidance, so check them against your own numbers.
- Effective federal funds rate (monthly average). FRED series FEDFUNDS; cross-checked vs Federal Reserve H.15 release (3.63% on 2026-06-30), 2026.
- Bank prime loan rate (WSJ prime equivalent). Federal Reserve H.15 Selected Interest Rates, 2026.
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