Solo 401(k) employer contribution — can you still fund it after year-end if the plan was opened in time?
ok so client opened his Solo 401(k) on Dec 20 2025 (just in time) and did a $5k employee deferral before year end. we're now in prep and he wants to add the employer nonelective contribution (25% of SE earnings basically).
my read is the employer piece has the extended due date — he can fund it through his 1040 due date incl extensions. employee deferral had to be in by 12/31 which he did.
anyone seen Fidelity or Schwab push back on a March funding for the employer piece? i feel like the custodian is usually the friction point not the IRS.
3 replies
employer side deadline is the extended due date — IRC §404(a)(6). you're fine.
Fidelity and Schwab both accept "employer contribution for prior year" categorisation as long as the contribution form has the plan year noted. the paperwork matters more than the calendar.
one gotcha: if he filed an extension make sure the contribution ACTUALLY hits by Oct 15. custodian "received" date is what the IRS cares about, not when he mailed the check.
good callout on the custodian received date. i'll tell him to wire not mail.
watching from the Irish side but just to note — if he ever moves here the equivalent PRSA contributions work very differently (hard calendar-year cap, no extended due date). worth knowing if he has international plans.
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