46 CFR 13.127: Service letters and transfer credit for tank endorsements

Last reviewed: October 14, 2026

This section sets out what a service letter must contain and who must sign it. It also sets rules for counting cargo or fuel oil transfers toward service and says when service on Articulated Tug Barges is creditable.

Applies toApplicants who submit service letters, including those seeking Tank Vessel-PIC, Tank Barge-PIC, Tank Vessel-Assistant, and Tank Vessel-Engineer endorsements.

What it says

  1. A service letter must be signed by the owner, operator, Master, or Chief Engineer of the vessel.

    46 CFR 13.127(a)“A service letter must be signed by the owner, operator, Master, or Chief Engineer of the vessel and must specify the following:”
  2. A service letter must give the name of the vessel, its official number, and the date of service for each vessel.

    46 CFR 13.127(a)(1)“The name of the vessel, official number for the vessel, and date of service for each vessel.”
  3. For Tank Vessel-PIC, Tank Barge-PIC, and Tank Vessel-Assistant endorsements, the letter must state the classification of cargo handled during the service (DL, LG, or, for a restricted endorsement, a specific product).

    46 CFR 13.127(a)(2)“the classification of cargo (DL, LG, or, for a restricted endorsement, a specific product) handled while the applicant accumulated the service.”
  4. For Tank Vessel-PIC or Tank Barge-PIC endorsements, the letter must state that the applicant has shown the signer they are fully capable of supervising liquid cargo transfers, including the listed steps.

    46 CFR 13.127(a)(4)“that the applicant has demonstrated to the satisfaction of the signer that they are fully capable of supervising transfers of liquid cargo, including—”
  5. A transfer must involve loading or discharge between at least one of the vessel's cargo tanks and a shore facility or another vessel. A shift of cargo from one tank to another is not a transfer.

    46 CFR 13.127(b)(1)“A shift of cargo from one tank to another tank is not a transfer for this purpose.”
  6. A transfer lasting beyond 4 hours still counts as only one transfer.

    46 CFR 13.127(b)(2)“Regardless of how long the transfer lasts beyond 4 hours, it counts as only one transfer.”
  7. A person may receive credit for only one transfer, one loading, and one discharge during each watch, regardless of how many tanks or products are involved.

    46 CFR 13.127(b)(4)“a person may receive credit for only one transfer, one loading, and one discharge conducted during each watch.”
  8. Service on ATBs with an aggregate tonnage of 1,600 GRT or more is creditable only case by case, with prior Coast Guard authorization, and only if the ATB equipment is comparable to tank vessel equipment.

    46 CFR 13.127(c)“Service on ATBs with an aggregate tonnage of 1,600 GRT or more will be creditable on a case-by-case basis and with prior authorization by the Coast Guard”

Common questions

Who can sign a service letter for a mariner credential?

The owner, operator, Master, or Chief Engineer of the vessel must sign the service letter.

“A service letter must be signed by the owner, operator, Master, or Chief Engineer of the vessel and must specify the following:”

Does a transfer longer than 4 hours count as more than one transfer?

No. A transfer counts as only one transfer regardless of how long it lasts beyond 4 hours.

“Regardless of how long the transfer lasts beyond 4 hours, it counts as only one transfer.”

Does moving cargo between tanks count as a transfer?

No. A shift of cargo from one tank to another tank is not a transfer for this purpose.

“A shift of cargo from one tank to another tank is not a transfer for this purpose.”

Can I get credit for service on an articulated tug barge?

Service on ATBs with an aggregate tonnage of 1,600 GRT or more is creditable case by case with prior Coast Guard authorization, if the ATB equipment is comparable to tank vessel equipment.

“provided the ATB equipment is comparable to tank vessel equipment. The Coast Guard may issue blanket authorizations for classes of ATBs.”

The text of 46 CFR 13.127

Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR

Service: General

(a) A service letter must be signed by the owner, operator, Master, or Chief Engineer of the vessel and must specify the following:

(1) The name of the vessel, official number for the vessel, and date of service for each vessel.

(2) For endorsements as Tank Vessel-PIC, Tank Barge-PIC, and Tank Vessel-Assistant, the classification of cargo (DL, LG, or, for a restricted endorsement, a specific product) handled while the applicant accumulated the service.

(3) The dates, the numbers and kinds of transfers the applicant has participated in, the ports or terminals, if applicable, and the number of transfers that involved commencement or completion of loading or discharge.

(4) For endorsements as Tank Vessel-PIC or Tank Barge-PIC, that the applicant has demonstrated to the satisfaction of the signer that they are fully capable of supervising transfers of liquid cargo, including—

(i) Pre-transfer inspection;

(ii) Pre-transfer conference and execution of the Declaration of Inspection;

(iii) Connection of cargo hoses or loading-arms;

(iv) Line-up of the cargo system for loading and discharge;

(v) Start of liquid flow during loading;

(vi) Start of cargo pump and increase of pressure to normal discharge pressure;

(vii) Calculation of loading-rates;

(viii) Monitoring;

(ix) Topping-off of cargo tanks during loading;

(x) Stripping of cargo tanks;

(xi) Ballasting and deballasting, if appropriate;

(xii) Disconnection of the cargo hoses or loading-arms; and

(xiii) Securing of cargo systems.

(5) For endorsements as Tank Vessel-Engineer, that the applicant has demonstrated to the satisfaction of the signer that they are fully capable of supervising transfers of fuel oil, including—

(i) Pre-transfer inspection;

(ii) Pre-transfer conference and execution of the Declaration of Inspection;

(iii) Connection of hoses or loading-arms;

(iv) Line-up of the piping system for loading and transfer of fuel oil;

(v) Start of liquid flow during loading;

(vi) Calculation of loading rates;

(vii) Monitoring;

(viii) Topping-off of tanks during loading;

(ix) Disconnection of the hoses or loading arms; and

(x) Securing of fuel oil systems.

(b) In determining the numbers and kinds of transfers that the applicant has participated in under paragraph (a)(3) of this section, the following rules apply:

(1) A transfer must involve the loading or discharge from at least one of the vessel's cargo tanks to or from a shore facility or another vessel. A shift of cargo from one tank to another tank is not a transfer for this purpose.

(2) Regardless of how long the transfer lasts beyond 4 hours, it counts as only one transfer.

(3) A transfer must include both a commencement and a completion.

(4) Regardless of how many tanks or products are being loaded or discharged at the same time, a person may receive credit for only one transfer, one loading, and one discharge conducted during each watch.

(5) Credit for a transfer during a watch of less than 4 hours accrues only if the watch includes either the connection and the commencement of transfer or the completion of transfer and the disconnection.

(6) Credit for a commencement of loading accrues only if the applicant participates in the pre-transfer inspection, the pre-transfer conference including execution of the Declaration of Inspection, the connection of hoses or loading-arms, the line-up of the system for the loading, the start of liquid flow, and the calculation of loading-rates, where applicable.

(7) Credit for a commencement of discharge accrues only if the applicant participates in the pre-transfer inspection, the pre-transfer conference including execution of the Declaration of Inspection, the connection of hoses or loading-arms, the line-up of the cargo system for the discharge, the start of the pump or pumps and increase of pressure to normal pressure for discharge, and the monitoring of discharge rates.

(8) Credit for a completion of transfer, whether loading or discharge, accrues only if the applicant participates in the topping-off at the loading port, or in the stripping of cargo tanks and the commencement of ballasting, if required by the vessel's transfer procedures, at the discharge port.

(9) Personnel desiring credit for transfers during off-duty hours may satisfy requirements of competence through incremental training periods that include segments of transfers. The cumulative number of transfers must equal the minimum specified in §§ 13.203(b) or 13.303(b) of this subchapter.

(c) Service on Articulated Tug Barges (ATBs). Service on ATBs with an aggregate tonnage of 1,600 GRT or more will be creditable on a case-by-case basis and with prior authorization by the Coast Guard, provided the ATB equipment is comparable to tank vessel equipment. The Coast Guard may issue blanket authorizations for classes of ATBs.

Sections it refers to

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.