Letters, Sub-Internships, and the Application Year

Part of Medical School. Fourth year is a second application cycle, and it is the one nobody prepared you for, because the first one at least had a public playbook. This is what a sub-internship is really testing, how letters get written and when to ask, what program signals are, and where the advising gap does the most damage.

The short version

The year runs on fixed national dates, and the ones that matter are earlier than most students assume. The application opens in June and goes to programs in early September.

A sub-internship is an audition, and it is scored as function rather than knowledge. The question being answered is whether you could be an intern in eleven months.

Letters are asked for in the spring before the summer they are due. The best letter writer is someone who watched you work, not someone with the most impressive title.

Signals are rationed and the allotment changes every year and every specialty. Look up your own field's number for your own cycle; nothing else is reliable.

The advising gap is the real inequality of this year. Students with a mentor in the field get told how many programs to apply to and which ones are realistic. Everyone else guesses, and guessing is expensive.

The calendar this year runs on

The dates are national and published, and the shape has been stable for several cycles even though the specific days move. For the 2027 season, which is the cycle a student graduating in 2027 applies in: the season opened 4 June 2026, applicants could begin submitting to programs on 2 September 2026, and programs could begin reviewing applications and MSPEs on 23 September 2026.¹

Everything you want in the application has to exist before early September. Letters, the personal statement, and your list of programs. A letter writer asked in August is a letter writer asked too late.

There is a three-week gap between when you submit and when anyone reads it. Submitting on the first possible day is fine and submitting a few days later is also fine. Submitting an incomplete application in a panic on day one is worse than either.

The rest of the year: interviews through autumn and winter, mostly virtual since 2020, rank-order lists due in February, and the algorithm in March. The Match, and What Happens If You Don't covers ranking and the week itself.

Dates shift each cycle. Check the current ERAS timeline for your own year rather than trusting any summary, including this one.

A sub-internship is an audition for a job

A sub-internship, usually called a sub-I, is a rotation where you carry the responsibilities of an intern under supervision: your own patients, your own notes, your own presentations, your own pages. Most students do one or two, in the field they are applying to, in the summer or early autumn of fourth year.

What it is testing is not what third year tested. Clerkships largely asked whether you knew things and were pleasant to work with. A sub-I asks a narrower question: could this person function as an intern next July? Reliability, ownership, and safe escalation matter more than being impressive.

That distinction turns into concrete behavior:

Own the patient rather than the presentation. Follow through on what you said you would do, chase the study, call the consultant, and know the plan before anyone asks.

Escalate early and without drama. The single most reassuring thing a student can demonstrate is knowing what they do not know and saying so quickly.

Write notes that someone could use. A note that the team actually keeps is a stronger signal than a well-delivered presentation.

Be the person who is there. Same rule as third year, higher stakes, because these are the people writing about you to a program that may hire you.

A sub-I at your own institution and one away carry different weight in different fields. In much of medicine a strong home sub-I is enough. In several surgical subspecialties and dermatology an away rotation is close to expected. Choosing a Specialty has that split and the cost picture, and Fourth Year has the money.

The spring conversation that produces your letters

Most applications carry three or four letters. Fields differ: some expect a departmental or chair's letter, some expect a specific number from within the specialty, and a few weight a research letter heavily. Find out your own field's convention from someone in it, early.

Ask in the spring, not the summer. Writers need weeks, they are writing several, and the good ones write better with time. Asking in March or April for a letter due in August is normal and welcome.

Ask the person who watched you work. An attending who supervised you day to day for four weeks and remembers specific cases writes a more useful letter than a division chief who met you twice. Program directors read for specificity and can tell the difference immediately.

Ask a real question, and listen to the answer. Do you feel you know my work well enough to write me a strong letter for this specialty? gives a hesitant writer an honorable exit, which is a gift to you. A lukewarm letter does more damage than a missing one.

Hand over material. Your CV, your personal statement draft, a short note reminding them of the specific patients or projects you worked on together, and the deadline. Every writer appreciates it and the letter gets better.

Waive your right to see it. Unwaived letters are read as weaker, and that is the convention whether or not it is fair.

The MSPE is a document about you, and you can usually read it first

Your school writes a Medical Student Performance Evaluation and sends it with your application. It summarizes your performance, quotes clerkship comments, and at many schools places you in a band or uses a set of coded descriptors that program directors read fluently. Information available by 1 October of the application year can be included, which is why fourth-year grades from early rotations sometimes appear in it.²

Most schools let students review a draft. Read yours, and read it as a stranger would.

You are generally not able to argue with a judgment you dislike. You are usually able to correct a factual error, a mis-transcribed grade, or a comment attributed to the wrong rotation. Students who never open the document cannot do either. Clerkships covers the evaluations that feed it and what to do about one that is wrong.

Why last year's signaling advice is wrong

Program signaling lets you flag a limited number of programs as genuinely preferred when you apply. It exists because programs were drowning in applications and had no way to tell real interest from a broad send.

The allotment varies enormously by specialty and changes annually. In the 2027 season, urology and orthopedic surgery applicants received 30 signals, some combined programs received 2, and several specialties split their allotment into tiers, with internal medicine at 3 gold and 12 silver and dermatology at 3 gold and 25 silver.³

Which means the only correct source is the current-cycle list for your own specialty. Advice from a graduate two years ahead of you is likely to be wrong in the specific way that costs you an interview, and that is not their fault.

The AAMC's own guidance is to signal the programs you are most interested in regardless of whether you rotated there.³ Beyond that, the useful judgment is about honesty with yourself: a signal spent on a program you would not attend is a signal wasted, and a signal withheld from a reach program out of embarrassment is also wasted.

The FLI version: the advising gap is what actually costs you

Every mechanical thing on this page is published somewhere. The part that is not published is the calibration, and it is where first-generation and low-income (FLI) students, the ones without a physician in the family, lose the most ground.

How many programs to apply to. The honest answer depends on your specialty, your record, and where you would be happy, and it is the single most consequential number in the year. Applying to too few risks the Match. Applying to far too many costs thousands of dollars in fees and buys very little. A mentor in the field gives you a range in one conversation. Without one, students routinely do both.

Which programs are realistic. Reading a program list without knowing the field's internal geography is nearly impossible, and this is the specific work a specialty advisor does.

Who makes a phone call. Some of what happens in this season happens between faculty. A mentor who calls a program on your behalf is doing something you cannot do for yourself, and students who have never had an advocate frequently do not know to ask for one. Research, Mentors, and Academic Currency covers building that relationship in time for it to matter.

Three things that close most of the gap, and all are available to anyone:

Meet your specialty's advisor at your school in the spring of third year, before the season starts. Ask the fourth-years in your field, in April, how many programs they applied to and how it went, because they are the only people with fresh calibration. And ask your student affairs dean directly whether your list looks reasonable for your record; it is their job, and they say yes to that question more often than students expect.

What interview season is actually like

Mostly virtual, mostly between October and January, and it is a heavier load than it sounds. Interviews cluster, they compete with rotations, and the scheduling itself is a race because slots open by email and fill in hours.

Practical things that matter more than they should: keep your phone on and your email open during release weeks, have a quiet room and a tested connection, and know that a bad connection is forgiven while an unprepared answer is not. Costs are lower than the travel era but not zero, and second-look visits, where they exist, are optional in principle and expensive in practice.

What belongs to other pages

Ranking, the algorithm, Match week, and SOAP are The Match, and What Happens If You Don't.

What fourth year costs, and the aid levers that exist for it, is Fourth Year.

How the specialty decision gets made, and how competitive a field really is, is Choosing a Specialty.

Clerkship evaluations and the comments that end up in the MSPE are Clerkships.

If a setback in third or fourth year changes the plan, that is Academic Setbacks and Alternate Paths.

Where this fits on the Road

The application year rewards early asking. Letters in the spring, an advisor conversation before the season opens, and the current-cycle signal rules rather than last year's. None of that requires connections you do not have, and all of it is the sort of thing that gets said at a dinner table in a family of doctors and nowhere else. This page exists so it gets said here instead.

ERAS dates, signal allotments, letter conventions, and MSPE practices change every cycle and vary by specialty and by school. Verify the current-year timeline and your own school's policies before relying on anything here. Educational information, not advice. — Last reviewed: 2026-08-09

References

AAMC, 2027 ERAS Residency Timeline. Verified 2026-08-03: the 2027 ERAS season began 4 June 2026 at 9 a.m. ET; residency applicants could begin submitting MyERAS applications to programs on 2 September 2026 at 9 a.m. ET; programs could begin reviewing applications and MSPEs on 23 September 2026 at 9 a.m. ET; the season ends 31 May 2027. ⟳ Verify current dates each cycle. https://students-residents.aamc.org/eras-tools-and-worksheets-residency-applicants/2027-eras-residency-timeline ↩
AAMC guidance on the Medical Student Performance Evaluation. Verified 2026-08-03: the MSPE may include any information available by 1 October of the year it is submitted, including fourth-year clerkship grades and evaluations. Whether students may review a draft, and the format of any comparative band or descriptor, are set by each school. https://students-residents.aamc.org/applying-residencies-eras/publication-chapters/medical-student-performance-evaluation-mspe-or-dean-s-letter ↩
AAMC, Program Signaling for the 2027 MyERAS Application Season. Verified 2026-08-03: signal allotments vary by specialty and several specialties use tiered signals. Examples from the 2027 list include urology and orthopedic surgery at 30 signals, internal medicine at 3 gold and 12 silver, and dermatology at 3 gold and 25 silver. The AAMC advises applicants to signal their most-preferred programs regardless of whether they rotated there. ⟳ Allotments change annually; check your own specialty for your own cycle. https://students-residents.aamc.org/applying-residencies-eras/program-signaling-2027-myeras-application-season ↩ ↩²