In the

United States Court of Appeals

For the Seventh Circuit

No. 99-3783

Mark F. Elmore,

Plaintiff-Appellant,

v.

William J. Henderson, Postmaster General,

Defendant-Appellee.

Appeal from the United States District Court

for the Southern District of Indiana, Indianapolis Division.

No. IP-98-1664-C-B/S--Sarah Evans Barker, Chief Judge.

Argued August 9, 2000--Decided September 14, 2000

 Before Posner, Ripple, and Williams, Circuit Judges.

 Posner, Circuit Judge. This appeal from the

dismissal of the plaintiff’s suit because the

statute of limitations had run presents a tangle

of important statute-of-limitations issues. The

plaintiff filed a suit along with two other

persons against the Postal Service charging

violations of Title VII and the Rehabilitation

Act. The suit was filed on February 23, 1998,

which, so far as Elmore was concerned, was the

84th day of the 90-day period within which the

suit had to be filed after the final decision by

the Postal Service turning down his

administrative complaint. 29 C.F.R. sec.

1614.407. The judge dismissed Elmore and one of

the other two plaintiffs, without prejudice, on

the ground of misjoinder because the three

plaintiffs’ claims did not arise out of the same

event or series of events. Fed. R. Civ. P. 20(a),

21; Intercon Research Associates, Ltd. v. Dresser

Industries, Inc., 696 F.2d 53, 57 (7th Cir.

1982); Alexander v. Fulton County, 207 F.3d 1303,

1323-24 (11th Cir. 2000); Abdullah v. Acands,

Inc., 30 F.3d 264, 268 n. 5 (1st Cir. 1994). That

was on August 5, 1998. After the remaining

plaintiff settled with the defendant, the judge

dismissed the entire suit with prejudice. That

was on October 22, 1999; earlier, on December 4,

1998, Elmore had refiled his claim as a separate

suit. The district judge dismissed the refiled

suit with prejudice because it had not been filed
within the six days remaining of the original

limitations period when Elmore was dismissed from

the suit or even within 90 days following that

dismissal. Elmore argues that because the

original suit was timely, his second suit should

have been treated simply as a continuation of the

original suit, especially since, he further

argues, the judge erred in dismissing him from

the original suit. Alternatively, he argues that

the running of the statute of limitations on the

second suit should be equitably tolled.

 The filing of a suit stops the running of the

statute of limitations, though only contingently.

It is true that if the suit is later dismissed

with prejudice, any issue concerning the bar of

the statute of limitations to the refiling of the

suit will be moot because a suit that has been

dismissed with prejudice cannot be refiled; the

refiling is blocked by the doctrine of res

judicata. But if the suit is dismissed without

prejudice, meaning that it can be refiled, then

the tolling effect of the filing of the suit is

wiped out and the statute of limitations is

deemed to have continued running from whenever

the cause of action accrued, without interruption

by that filing. E.g., Conover v. Lien, 87 F.3d

905, 908-09 (7th Cir. 1996); Beck v. Caterpillar

Inc., 50 F.3d 405, 407 (7th Cir. 1995); Powell v.

Starwalt, 866 F.2d 964, 966 (7th Cir. 1989);

Chico-Velez v. Roche Products, Inc., 139 F.3d 56,

59 (1st Cir. 1998); Johnson v. Nyack Hospital, 86

F.3d 8, 11 (2d Cir. 1996); Garfield v. J.C.

Nichols Real Estate, 57 F.3d 662, 666 (8th Cir.

1995).

 In other words, a suit dismissed without

prejudice is treated for statute of limitations

purposes as if it had never been filed. E.g.,

Beck v. Caterpillar Inc., supra, 50 F.3d at 407;

Lambert v. United States, 44 F.3d 296, 298 (5th

Cir. 1995); Dade County v. Rohr Industries, Inc.,

826 F.2d 983, 989 (11th Cir. 1987). Were this not

the rule, statutes of limitations would be easily

nullified. The plaintiff could file a suit,

dismiss it voluntarily the next day, and have

forever to refile it. The strongest case for the

rule that the running of the statute of

limitations is unaffected by a dismissal without

prejudice is therefore the case in which the

plaintiff procured the dismissal, as by

voluntarily dismissing the suit. See, e.g.,

Willard v. Wood, 164 U.S. 502, 523 (1896); Beck

v. Caterpillar Inc., supra, 50 F.3d at 407;

Bonneville Associates, Limited Partnership v.

Barram, 165 F.3d 1360, 1364 (Fed. Cir. 1999). But

that cannot place limits on the scope of the

rule, since a plaintiff can almost always

precipitate a dismissal without prejudice, for

example by failing to serve the defendant
properly or by failing to allege federal

jurisdiction, even if he does not move to dismiss

it. The rule is therefore as we stated it: when a

suit is dismissed without prejudice, the statute

of limitations is deemed unaffected by the filing

of the suit, so that if the statute of

limitations has run the dismissal is effectively

with prejudice. E.g., Duffy v. Ford Motor Co.,

218 F.3d 623, 629 (6th Cir. 2000); Hatchett v.

Nettles, 201 F.3d 651, 652-53 (5th Cir. 2000)

(per curiam). The severity of the rule is

mitigated, however, by the doctrine of equitable

tolling, as we’ll see.

 When there are several plaintiffs in a single

suit and one is dismissed out, whether under Rule

21 or any other rule or doctrine, it is as if he

had brought a separate suit that was dismissed.

We cannot find a case on the point; but it seems

to us clear as a matter of first principles. The

purpose of Rule 20(a) in permitting joinder in a

single suit of persons who have separate claims,

albeit growing out of a single incident,

transaction, or series of events, is to enable

economies in litigation, not to merge the

plaintiffs’ rights so that the defendant loses

defenses that he might have had against one of

the plaintiffs. It is true that the statute of

limitations is tolled for class members until it

is determined that the case cannot proceed as a

class action, Crown, Cork & Seal Co. v. Parker,

462 U.S. 345, 352-53 (1983); American Pipe &

Construction Co. v. Utah, 414 U.S. 538, 551-52

(1974); Hemenway v. Peabody Coal Co., 159 F.3d

255, 265-66 (7th Cir. 1998), but that is because

a class action is not a mere "invitation to

joinder." American Pipe & Construction Co. v.

Utah, supra, 414 U.S. at 550. It is a device

centrally concerned with the economies of

aggregating small claims, and it would thus be

seriously impaired by a rule that required all

the class members to file separate, protective

suits, against the eventuality that the statute

of limitations would run during the period when

the class status of the putative class action

remained undetermined. We want the class members

to rely on the filing of the class action rather

than to clutter the courts with a multitude of

separate suits.

 There is in any event little risk that a

determination that claims have been misjoined

will lead to a dismissal with statute of

limitations consequences, since, as we’re about

to see, the district court is duty-bound to

prevent those consequences by severing rather

than dismissing claims. If it fails in that duty,

the remedy is appeal.

 Hence the dismissal of Elmore from the suit on
August 5, 1998, occurred long after the 90-day

period within which he had to sue had elapsed,

and was time barred before that date, not six,

let alone 96, days later. Cf. Wilson v. Grumman

Ohio Corp., 815 F.2d 26, 27-28 (6th Cir. 1987)

(per curiam). The judge erred in thinking that

the statute of limitations was tolled between the

filing of the original suit and when she

dismissed Elmore from it.

 It is irrelevant that the dismissal was almost

certainly erroneous, not because there wasn’t

misjoinder, but because in formulating a remedy

for a misjoinder the judge is required to avoid

gratuitous harm to the parties, including the

misjoined party. Rule 21 not only requires that

orders adding or dropping parties be made "on

such terms as are just," but also expressly

allows the judge to sever the misjoined party’s

claim rather than dismiss it. Sabolsky v.

Budzanoski, 457 F.2d 1245, 1249 (3d Cir. 1972).

The judge could and should have allowed Elmore’s

claim against the Postal Service to continue as a

separate suit so that it would not be timebarred. Rice v. Sunrise Express, 209 F.3d 1008,

1014 n. 8 (7th Cir. 2000); White v. ABCO

Engineering Corp., 199 F.3d 140, 145 n. 6 (3d

Cir. 1999). As an offshoot of the original suit,

Elmore’s separate, severed suit, though separate

from the original suit for other purposes, would

not have affected the tolling of the statute of

limitations by the original suit. That is, it

would have been a continuation of the original

suit so far as he was concerned. This would be

obvious if the judge had dismissed the other two

plaintiffs from the suit, leaving Elmore as the

sole plaintiff, rather than dismissing Elmore and

one of the two other plaintiffs; and we do not

think the running of the statute of limitations

should be affected by which joined plaintiffs are

dismissed.

 But waiving the statute of limitations is not

the proper remedy for an erroneous dismissal. The

proper remedy is appeal. Although the suit

continued in the district court on behalf of the

remaining plaintiff, and so the dismissal of

Elmore was not a final judgment in the usual

sense, Rule 54(b) allows the district judge to

enter a final, immediately appealable judgment

from an order that dismisses one of the parties.

See House v. Belford, 956 F.2d 711, 716 (7th Cir.

1992); In re Southeast Banking Corp., 69 F.3d

1539, 1547 (11th Cir. 1995); Haynesworth v.

Miller, 820 F.2d 1245, 1252-53 (D.C. Cir. 1987).

Elmore did not ask for such a judgment.

 So the statute of limitations ran long before

Elmore refiled his suit. That in itself need not

have been fatal. There are defenses to the
statute of limitations, and Elmore is right in

identifying equitable tolling as one of them. The

running of a statute of limitations can be

equitably tolled when through no fault of his own

the plaintiff was unable to sue within the

limitations period but he sued as soon as he

could. E.g., Flight Attendants Against UAL Offset

v. Commissioner, 165 F.3d 572, 575-76 (7th Cir.

1999); Donald v. Cook County Sheriff’s Dept., 95

F.3d 548, 561-62 (7th Cir. 1996); Cada v. Baxter

Healthcare Corp., 920 F.2d 446, 451 (7th Cir.

1990); Graham-Humphreys v. Memphis Brooks Museum

of Art, Inc., 209 F.3d 552, 560-61 (6th Cir.

2000). This, however, is not a case in which the

plaintiff was prevented from suing within the

limitations period. He did sue within that

period. His complaint is that his suit was

erroneously dismissed, as a result of which,

though the dismissal was without prejudice, his

claim was lost because the statute of limitations

ran before he refiled. Equitable tolling is not a

remedy for an erroneous judgment; appeal, or in

exceptional cases a motion under Fed. R. Civ. P.

60, is.

 For completeness we note that, even if equitable

tolling could do service here for an appeal, as

assumed (rather than discussed) in Justice v.

United States, 6 F.3d 1474, 1480-82 (11th Cir.

1993), the doctrine would be unavailable to

Elmore in the circumstances of this case. It is

true that he cannot be faulted for having failed

to refile his suit before the district court

dismissed him from the original one. He had no

reason to anticipate an erroneous order

dismissing him for misjoinder rather than just

severing his claim and allowing it to continue as

a separate suit. But he could not possibly invoke

the doctrine of equitable tolling unless he sued

just as soon as possible after the judge’s action

made him realize that the statute of limitations

had run. He waited four months to sue and has

offered no excuse for the delay. Since all he had

to do was refile the original complaint, merely

deleting reference to his coplaintiff’s claims,

it is not surprising that he is unable to come up

with an excuse.

 We have emphasized in previous cases the social

importance of limitations periods for suing.

E.g., Cook v. City of Chicago, 192 F.3d 693, 696

(7th Cir. 1999); Galloway v. General Motors

Service Parts Operations, 78 F.3d 1164, 1165-66

(7th Cir. 1996); see also Delaware State College

v. Ricks, 449 U.S. 250, 259-60 (1980); Dring v.

McDonnell Douglas Corp., 58 F.3d 1323, 1330 (8th

Cir. 1995). Such deadlines minimize legal

uncertainty both about the outcome of eventual

litigation and about the existence and scope of

the potential defendant’s liability. Burnett v.
New York Central R.R., 380 U.S. 424, 428 (1965);

Bailey v. International Brotherhood of

Boilermakers, Etc., Local 374, 175 F.3d 526, 531

(7th Cir. 1999); Servicios-Expoarma, C.A. v.

Industrial Maritime Carriers, Inc., 135 F.3d 984,

989 (5th Cir. 1998); Sperling v. Hoffmann-La

Roche, Inc., 24 F.3d 463, 471-72 (3d Cir. 1994).

The importance of the limitations period in the

present case is underscored by the brevity of

that period. By fixing 90 days as the deadline

for suing after final agency action, the Postal

Service has emphasized the urgency of prompt

resolution of employment claims against it. The

practical reason for that sense of urgency in an

employment case is that an employer’s liability

tends to mount up with each day that judgment is

deferred, since back pay (in a dismissal case)

accumulates from the dismissal of the plaintiff

to his reinstatement following the entry of a

judgment for him. Cook v. City of Chicago, supra,

192 F.3d at 696; Cada v. Baxter Healthcare Corp.,

supra, 920 F.2d at 452-53.

Affirmed.