Short answer: The Merchandise Processing Fee (MPF) and Harbor Maintenance Fee (HMF) are US government fees charged on imports in addition to duties. MPF funds customs processing and is calculated as a percentage of the shipment's value with a minimum and maximum cap; HMF funds port maintenance and applies to ocean shipments as a percentage of cargo value with no cap. For DTC brands, these fees are small per shipment but add up across thousands of parcels, and misunderstanding the caps is one of the most common landed-cost errors. MPF has a floor and ceiling per entry, HMF does not, and both have exemptions worth knowing.
What the MPF covers and how it is calculated
The MPF pays for the customs processing of your import: the systems, the officers, the infrastructure that clears your goods. It is assessed as a percentage of the entered value, currently 0.3464 percent, with a minimum and maximum per entry that adjust periodically for inflation. The minimum means even a tiny shipment pays a few dollars; the maximum means a very large shipment stops paying more past the cap.
The per-entry structure is what matters for planning. Because the fee applies per entry with a floor and ceiling, how you consolidate shipments changes the total. Ten separate entries each pay the minimum; one consolidated entry pays once, possibly hitting the cap. For DTC brands shipping parcels individually, the minimum applies constantly, which makes MPF a meaningful line item at scale even though the percentage looks trivial.
What the HMF covers and how it differs
The Harbor Maintenance Fee funds the maintenance of US ports and harbors: dredging, upkeep, the physical infrastructure ocean freight depends on. It applies to ocean shipments at 0.125 percent of cargo value, and unlike MPF it has no maximum. A high-value ocean shipment pays HMF in full on the entire value, which surprises brands that assume all fees cap out.
HMF applies to ocean imports including those admitted to foreign trade zones, and it is collected by CBP along with duties. It does not apply to air shipments, which is one of the quiet cost differences between ocean and air freight that goes beyond the freight rate itself. When brands compare ocean versus air landed cost, HMF belongs in the ocean column, and on high-value goods it is not negligible.
Exemptions and special cases
Both fees have exemptions that DTC brands should verify rather than assume. Goods from certain trade preference programs may be exempt from MPF, and the rules differ by program, so the exemption depends on the claim you are making, not just the origin country. Informal entries, the simplified process for low-value shipments, have their own MPF treatment with a flat fee instead of the percentage calculation.
The de minimis threshold interacts here too: shipments entering under the duty-free de minimis value generally avoid these fees as well, which is part of why the effective landed cost of a de minimis parcel is so much lower than a formally entered one. But relying on de minimis as a fee strategy is fragile, since thresholds and enforcement change. Know the exemptions, but build your cost model on the standard case.
Getting the fees right in landed cost
The most common error is modeling MPF as a flat percentage with no caps, which overstates the fee on large consolidated shipments and understates it on small ones hitting the minimum. The second most common error is forgetting HMF entirely on ocean freight, which is easy to do because it is not a duty and does not appear in duty calculators. Both errors compound across thousands of shipments.
Build the fees into your landed-cost model as separate line items with the current rates, floor, and ceiling, and review them when CBP adjusts the numbers. Your customs broker's entry summaries show the actual MPF and HMF paid per entry, so reconcile the model against real entries quarterly. The fees are not where the big savings are, but they are where the quiet modeling errors live, and accurate landed cost starts with getting every line right.
Do MPF and HMF apply to every import?
Nearly. MPF applies to formal entries with limited exemptions for certain trade programs. HMF applies to ocean shipments. Informal entries and de minimis shipments are generally outside both. If you are formally entering goods by ocean, assume both apply.
Who actually pays these fees?
The importer of record pays, as part of the entry. For DTC brands shipping DDP, that cost sits with whoever holds the IOR role, usually the brand or its agent, and it should be baked into the landed-cost math behind the checkout price, not passed through as a surprise.
How often do the rates change?
The MPF percentage is set by statute and changes rarely, but the minimum and maximum are adjusted for inflation periodically. HMF has been stable for years. Check CBP's published figures when you build or refresh your landed-cost model rather than relying on last year's numbers.